Shadow Cube Tutorial

Windows (DirectX 12)	Linux (Vulkan)	MacOS (Metal)	iOS (Metal)

This tutorial demonstrates rendering shadow of the textured cube on the floor plane in two render passes using Methane Kit:

Tutorial demonstrates using of the following Methane Kit features additionally to features demonstrated in TexturedCube tutorial:

Render with multiple render passes;
Use texture as render target attachment in one pass and as an input program binding in another pass;
Compile and loading shaders code with macro-definitions to render state programs;
Use graphics extension MeshBuffers and TexturedMeshBuffers classes to simplify mesh rendering code;
Simple shadows rendering technique. See detailed technique description here

Application Controls

Common keyboard controls are enabled by the Platform, Graphics and UserInterface application controllers:

Application and Frame Class Definitions

ShadowCubeApp class is declared in header file ShadowCubeApp.h and the application class is derived from UserInterface::App base class, same as in previous tutorial. Shaders/ShadowCubeUniforms.h header contains declaration of shader uniform structures shared between HLSL shader code and C++:

Constants data structure is stored in the m_scene_constants member and is uploaded into the Rhi::Buffer object m_const_buffer_ptr, which has single instance in application since its data is constant for all frames.
SceneUniforms data structure is stored in the m_scene_uniforms member and is uploaded into the Rhi::Buffer objects in the per-frame ShadowCubeFrame objects, each with it's own state of volatile uniform values.
MeshUniforms data structure contains Model/MVP matrices and shadow MVP+Transform matrix stored in 4 instances: uniforms for shadow and final passes stored in gfx::TexturedMeshBuffers objects one for cube mesh in m_cube_buffers_ptr and one for floor mesh in m_floor_buffers_ptr.

Uniform structures in Shaders/ShadowCubeUniforms.h:

struct Constants
{
    float4 light_color;
    float  light_power;
    float  light_ambient_factor;
    float  light_specular_factor;
};

struct SceneUniforms
{
    float4 eye_position;
    float3 light_position;
};

struct MeshUniforms
{
    float4x4 model_matrix;
    float4x4 mvp_matrix;
#ifdef ENABLE_SHADOWS
    float4x4 shadow_mvpx_matrix;
#endif
};

MeshBuffers.hpp implements auxiliary class TexturedMeshBuffers<UniformsType> which is managing vertex, index, uniforms buffers and texture with data for particular mesh drawing passed to constructor as a reference to BaseMesh object.

Supplementary member m_scene_uniforms_subresource stores a pointer to the m_scene_uniforms in the std::vector type gfx::IResource::SubResources which is passed to Rhi::Buffer::SetData(...) method to update the buffer data on GPU.

Two gfx::Camera objects are used: one m_view_camera is usual perspective view camera, while the other m_light_camera is a directional light camera with orthogonal projection used to generate transformation matrix from view to light coordinate systems.

Also, there are two Rhi::Sampler objects: one is used for sampling cube and floor textures, while the other is used for sampling shadow map texture.

#pragma once

#include <Methane/Kit.h>
#include <Methane/UserInterface/App.hpp>

namespace hlslpp
{
#define ENABLE_SHADOWS
#pragma pack(push, 16)
#include "Shaders/ShadowCubeUniforms.h"
#pragma pack(pop)
}

namespace Methane::Tutorials
{

namespace gfx = Methane::Graphics;
namespace rhi = Methane::Graphics::Rhi;

struct ShadowCubeFrame final : gfx::AppFrame
{
    ...
};

using UserInterfaceApp = UserInterface::App<ShadowCubeFrame>;

class ShadowCubeApp final : public UserInterfaceApp
{
   ...

private:
    using TexturedMeshBuffersBase = gfx::TexturedMeshBuffers<hlslpp::MeshUniforms>;
    class TexturedMeshBuffers : public TexturedMeshBuffersBase
    {
    public:
        using TexturedMeshBuffersBase::TexturedMeshBuffersBase;

        void SetShadowPassUniforms(hlslpp::MeshUniforms&& uniforms) noexcept { m_shadow_pass_uniforms = std::move(uniforms); }

        [[nodiscard]] const hlslpp::MeshUniforms& GetShadowPassUniforms() const noexcept             { return m_shadow_pass_uniforms; }
        [[nodiscard]] const rhi::SubResources&    GetShadowPassUniformsSubresources() const noexcept { return m_shadow_pass_uniforms_subresources; }

    private:
        hlslpp::MeshUniforms m_shadow_pass_uniforms{};
        rhi::SubResources    m_shadow_pass_uniforms_subresources{
            { reinterpret_cast<Data::ConstRawPtr>(&m_shadow_pass_uniforms), sizeof(hlslpp::MeshUniforms) } // NOSONAR
        };
    };

    struct RenderPassState
    {
        RenderPassState(bool is_final_pass, const std::string& command_group_name);
        void Release();

        const bool                       is_final_pass;
        const rhi::CommandListDebugGroup debug_group;
        rhi::RenderState                 render_state;
        rhi::ViewState                   view_state;
    };

    bool Animate(double elapsed_seconds, double delta_seconds);
    void RenderScene(const RenderPassState& render_pass, const ShadowCubeFrame::PassResources& render_pass_resources) const;

    const float                 m_scene_scale = 15.F;
    const hlslpp::Constants     m_scene_constants{
        { 1.F, 1.F, 0.74F, 1.F }, // - light_color
        700.F,                    // - light_power
        0.04F,                    // - light_ambient_factor
        30.F                      // - light_specular_factor
    };
    hlslpp::SceneUniforms    m_scene_uniforms{ };
    rhi::SubResources        m_scene_uniforms_subresource{
        { reinterpret_cast<Data::ConstRawPtr>(&m_scene_uniforms), sizeof(hlslpp::SceneUniforms) } // NOSONAR
    };
    gfx::Camera              m_view_camera;
    gfx::Camera              m_light_camera;
    rhi::Buffer              m_const_buffer;
    rhi::Sampler             m_texture_sampler;
    rhi::Sampler             m_shadow_sampler;
    Ptr<TexturedMeshBuffers> m_cube_buffers_ptr;
    Ptr<TexturedMeshBuffers> m_floor_buffers_ptr;
    rhi::RenderPattern       m_shadow_pass_pattern;
    RenderPassState          m_shadow_pass { false, "Shadow Render Pass" };
    RenderPassState          m_final_pass  { true,  "Final Render Pass" };
};

} // namespace Methane::Tutorials

ShadowCubeFrame struct contains frame-dependent volatile resources:

Shadow & final pass resources in shadow_pass and final_pass:
- Mesh resources for cube and floor:
  - Mesh uniforms buffer uniforms_buffer
  - Program bindings configuration program_bindings
- Render target texture rt_texture
- Render pass setup object render_pass
- Render command list cmd_list
Scene uniforms buffer in scene_uniforms_buffer
Command list set for execution on frame, which contains command lists from shadow and final passes.

struct ShadowCubeFrame final : gfx::AppFrame
{
    struct PassResources
    {
        struct MeshResources
        {
            rhi::Buffer          uniforms_buffer;
            rhi::ProgramBindings program_bindings;
        };

        MeshResources          cube;
        MeshResources          floor;
        rhi::Texture           rt_texture;
        rhi::RenderPass        render_pass;
        rhi::RenderCommandList cmd_list;
    };

    PassResources       shadow_pass;
    PassResources       final_pass;
    rhi::Buffer         scene_uniforms_buffer;
    rhi::CommandListSet execute_cmd_list_set;

    using gfx::AppFrame::AppFrame;
};

Graphics Resources Initialization

Initialization of textures, buffers and samplers is mostly the same as for Textured Cube tutorial, so we skip their description here.

Final pass render state initialization has some differences:

Pixel and vertex shaders are loaded for specific combination of macro definitions used during compilation during build. This macro definitions set is described in rhi::Shader::MacroDefinitions variable textured_shadows_definitions which is passed to rhi::Program::ShaderSet description structure.
Configuration of rhi::ProgramArgumentAccessors is more complex than for simple cube mesh and mostly describes Pixel-shader specific argument accessor types, except g_mesh_uniforms for Vertex-shader. g_constants, g_shadow_sampler, g_texture_sampler arguments are used with Constant type, g_scene_uniforms and g_shadow_map arguments are used with FrameConstant type while others have Mutable type, meaning that they can bind to different resources for different draw calls of any frame.

    // ========= Final Pass Render & View States =========

    const rhi::Shader::EntryFunction    vs_main{ "ShadowCube", "CubeVS" };
    const rhi::Shader::EntryFunction    ps_main{ "ShadowCube", "CubePS" };
    const rhi::Shader::MacroDefinitions textured_shadows_definitions{ { "ENABLE_SHADOWS", "" }, { "ENABLE_TEXTURING", "" } };

    // Create final pass rendering state with program
    rhi::RenderState::Settings final_state_settings
    {
        render_context.CreateProgram(
            rhi::Program::Settings
            {
                rhi::Program::ShaderSet
                {
                    { rhi::ShaderType::Vertex, { Data::ShaderProvider::Get(), vs_main, textured_shadows_definitions } },
                    { rhi::ShaderType::Pixel,  { Data::ShaderProvider::Get(), ps_main, textured_shadows_definitions } },
                },
                rhi::ProgramInputBufferLayouts
                {
                    rhi::Program::InputBufferLayout
                    {
                        rhi::Program::InputBufferLayout::ArgumentSemantics { cube_mesh.GetVertexLayout().GetSemantics() }
                    }
                },
                rhi::ProgramArgumentAccessors
                {
                    { { rhi::ShaderType::Vertex, "g_mesh_uniforms"  }, rhi::ProgramArgumentAccessor::Type::Mutable       },
                    { { rhi::ShaderType::Pixel,  "g_scene_uniforms" }, rhi::ProgramArgumentAccessor::Type::FrameConstant },
                    { { rhi::ShaderType::Pixel,  "g_constants"      }, rhi::ProgramArgumentAccessor::Type::Constant      },
                    { { rhi::ShaderType::Pixel,  "g_shadow_map"     }, rhi::ProgramArgumentAccessor::Type::FrameConstant },
                    { { rhi::ShaderType::Pixel,  "g_shadow_sampler" }, rhi::ProgramArgumentAccessor::Type::Constant      },
                    { { rhi::ShaderType::Pixel,  "g_texture"        }, rhi::ProgramArgumentAccessor::Type::Mutable       },
                    { { rhi::ShaderType::Pixel,  "g_texture_sampler"}, rhi::ProgramArgumentAccessor::Type::Constant      },
                },
                GetScreenRenderPattern().GetAttachmentFormats()
            }
        ),
        GetScreenRenderPattern()
    };
    final_state_settings.depth.enabled = true;

    m_final_pass.render_state = render_context.CreateRenderState( final_state_settings);
    m_final_pass.view_state = GetViewState();

rhi::RenderPattern class is used to define specific color/depth/stencil attachments configuration including their formats, load and store actions, without relation to specific resources used for attachments (this relation is set with rhi::RenderPass objects). Shadow pass pattern uses only depth attachment which is cleared on load and stored for further use in final screen render pass. The pattern also defines render pass access to shader resources and is marked with intermediate pass flag.

    // ========= Shadow Pass Render & View States =========

    // Create shadow-pass render pattern
    m_shadow_pass_pattern = render_context.CreateRenderPattern({
        { }, // No color attachments
        rhi::IRenderPattern::DepthAttachment(
            0U, context_settings.depth_stencil_format, 1U,
            rhi::RenderPassAttachment::LoadAction::Clear,
            rhi::RenderPassAttachment::StoreAction::Store,
            context_settings.clear_depth_stencil->first
        ),
        std::nullopt, // No stencil attachment
        rhi::RenderPassAccessMask(rhi::RenderPassAccess::ShaderResources),
        false // intermediate render pass
    });

Shadow pass render state is using the same shader code, but compiled with a different macro definitions set textured_definitions and thus the result program having different set of arguments available. Also note that the program include only Vertex shader since it will be used for rendering to depth buffer only without color attachment.

    // Create shadow-pass rendering state with program
    const rhi::Shader::MacroDefinitions textured_definitions{ { "ENABLE_TEXTURING", "" } };
    rhi::RenderState::Settings shadow_state_settings
    {
        render_context.CreateProgram(
            rhi::Program::Settings
            {
                rhi::Program::ShaderSet
                {
                    { rhi::ShaderType::Vertex, { Data::ShaderProvider::Get(), vs_main, textured_definitions } },
                },
                final_state_settings.program.GetSettings().input_buffer_layouts,
                rhi::ProgramArgumentAccessors
                {
                    { { rhi::ShaderType::Vertex, "g_mesh_uniforms" }, rhi::ProgramArgumentAccessor::Type::Mutable },
                },
                m_shadow_pass_pattern.GetAttachmentFormats()
            }
        ),
        m_shadow_pass_pattern
    };
    shadow_state_settings.depth.enabled = true;
    m_shadow_pass.render_state = render_context.CreateRenderState( shadow_state_settings);

The Shadow-pass view state is bound to the size of the Shadow-map texture:

    m_shadow_pass.view_state = rhi::ViewState({
        { gfx::GetFrameViewport(g_shadow_map_size)    },
        { gfx::GetFrameScissorRect(g_shadow_map_size) }
    });

Frame-dependent resources are initialized for each frame in loop. Execution command list set includes two command lists: one for shadow pass rendering and another for final pass rendering.

    for(ShadowCubeFrame& frame : GetFrames())
    {
        // Create uniforms buffer with volatile parameters for the whole scene rendering
        frame.scene_uniforms_buffer = render_context.CreateBuffer(rhi::BufferSettings::ForConstantBuffer(scene_uniforms_data_size, false, true));

        // ========= Shadow Pass Resources =========
        ...

        // ========= Final Pass Resources =========
        ...

        // Rendering command lists sequence
        frame.execute_cmd_list_set = rhi::CommandListSet({
            frame.shadow_pass.cmd_list.GetInterface(),
            frame.final_pass.cmd_list.GetInterface()
        }, frame.index);
    }

Shadow-map render target texture frame.shadow_pass.rt_texture_ptr is created for each frame using common setting with depth-stencil format taken from render context settings. Shadow-map texture settings also specify Usage bit-mask with RenderTarget and ShaderRead flags to allow both rendering to this texture and sampling from it in a final pass:

    const rhi::Texture::Settings shadow_texture_settings = rhi::Texture::Settings::ForDepthStencil(
        gfx::Dimensions(g_shadow_map_size),
        context_settings.depth_stencil_format, context_settings.clear_depth_stencil,
        rhi::ResourceUsageMask({ rhi::ResourceUsage::RenderTarget, rhi::ResourceUsage::ShaderRead })
    );

Volatile uniform buffers frame.shadow_pass.[floor|cube].uniforms_buffer are created separately for cube and floor meshes both for shadow and final passes rendering. Program bindings are created both for cube and floor meshes, which are binding created uniform buffers to the g_mesh_uniforms program argument of All shader types (taking into account that there's only Vertex shader in that program).

Shadow render pass frame.shadow_pass.render_pass is created without color attachments, but with depth attachment bound to the shadow-map texture for the current frame frame.shadow_pass.rt_texture. Depth attachment is crated with Clear load action to clear the depth texture with provided depth value, taken from render context settings context_settings.clear_depth_stencil->first; and Store action is used to retain rendered depth texture content for the next render pass. Render command list is created bound to the shadow render pass.

        // ========= Shadow Pass Resources =========
        
        // Create uniforms buffer for Cube rendering in Shadow pass
        frame.shadow_pass.cube.uniforms_buffer = render_context.CreateBuffer(rhi::BufferSettings::ForConstantBuffer(mesh_uniforms_data_size, false, true));
        
        // Create uniforms buffer for Floor rendering in Shadow pass
        frame.shadow_pass.floor.uniforms_buffer = render_context.CreateBuffer(rhi::BufferSettings::ForConstantBuffer(mesh_uniforms_data_size, false, true));
        
        // Shadow-pass resource bindings for cube rendering
        frame.shadow_pass.cube.program_bindings = shadow_state_settings.program.CreateBindings({
            { { rhi::ShaderType::Vertex, "g_mesh_uniforms" }, { { frame.shadow_pass.cube.uniforms_buffer.GetInterface() } } },
        }, frame.index);
        
        // Shadow-pass resource bindings for floor rendering
        frame.shadow_pass.floor.program_bindings = shadow_state_settings.program.CreateBindings({
            { { rhi::ShaderType::Vertex, "g_mesh_uniforms" }, { { frame.shadow_pass.floor.uniforms_buffer.GetInterface() } } },
        }, frame.index);
        
        // Create depth texture for shadow map rendering
        frame.shadow_pass.rt_texture = render_context.CreateTexture(shadow_texture_settings);
        
        // Create shadow pass configuration with depth attachment
        frame.shadow_pass.render_pass = m_shadow_pass_pattern.CreateRenderPass({
            { frame.shadow_pass.rt_texture.GetInterface() },
            shadow_texture_settings.dimensions.AsRectSize()
        });
        
        // Create render pass and command list for shadow pass rendering
        frame.shadow_pass.cmd_list = render_cmd_queue.CreateRenderCommandList(frame.shadow_pass.render_pass);

The same resources are created for the final render pass: uniform buffers for cube and floor meshes. Program bindings are created for cube and floor rendering too but with more complex set of program arguments, because final pass rendering program includes pixel and vertex shaders, but not only vertex shader like in shadow pass.

Render target texture is bound to frame screen texture i.e. frame buffer in swap-chain. Final render pass is also bound to the screen render pass for the current frame, which is created by base graphics application class Methane::Graphics::App. Render command list is created bound to the final render pass.

        // ========= Final Pass Resources =========

        // Create uniforms buffer for Cube rendering in Final pass
        frame.final_pass.cube.uniforms_buffer = render_context.CreateBuffer(rhi::BufferSettings::ForConstantBuffer(mesh_uniforms_data_size, false, true));

        // Create uniforms buffer for Floor rendering in Final pass
        frame.final_pass.floor.uniforms_buffer = render_context.CreateBuffer(rhi::BufferSettings::ForConstantBuffer(mesh_uniforms_data_size, false, true));

        // Final-pass resource bindings for cube rendering
        frame.final_pass.cube.program_bindings = final_state_settings.program.CreateBindings({
            { { rhi::ShaderType::Vertex, "g_mesh_uniforms"  }, { { frame.final_pass.cube.uniforms_buffer.GetInterface()  } } },
            { { rhi::ShaderType::Pixel,  "g_scene_uniforms" }, { { frame.scene_uniforms_buffer.GetInterface()            } } },
            { { rhi::ShaderType::Pixel,  "g_constants"      }, { { m_const_buffer.GetInterface()                         } } },
            { { rhi::ShaderType::Pixel,  "g_shadow_map"     }, { { frame.shadow_pass.rt_texture.GetInterface()           } } },
            { { rhi::ShaderType::Pixel,  "g_shadow_sampler" }, { { m_shadow_sampler.GetInterface()                       } } },
            { { rhi::ShaderType::Pixel,  "g_texture"        }, { { m_cube_buffers_ptr->GetTexture().GetInterface()       } } },
            { { rhi::ShaderType::Pixel,  "g_texture_sampler"}, { { m_texture_sampler.GetInterface()                      } } },
        }, frame.index);

        // Final-pass resource bindings for floor rendering - patched a copy of cube bindings
        frame.final_pass.floor.program_bindings = rhi::ProgramBindings(frame.final_pass.cube.program_bindings, {
            { { rhi::ShaderType::Vertex, "g_mesh_uniforms"  }, { { frame.final_pass.floor.uniforms_buffer.GetInterface() } } },
            { { rhi::ShaderType::Pixel,  "g_texture"        }, { { m_floor_buffers_ptr->GetTexture().GetInterface()      } } },
        }, frame.index);

        // Bind final pass RT texture and pass to the frame buffer texture and final pass.
        frame.final_pass.rt_texture  = frame.screen_texture;
        frame.final_pass.render_pass = frame.screen_pass;
        
        // Create render pass and command list for final pass rendering
        frame.final_pass.cmd_list = render_cmd_queue.CreateRenderCommandList(frame.final_pass.render_pass);

        // Rendering command lists sequence
        frame.execute_cmd_list_set = rhi::CommandListSet({
            frame.shadow_pass.cmd_list.GetInterface(),
            frame.final_pass.cmd_list.GetInterface()
        }, frame.index);

When render context is going to be released, all related resources must be released before that. This is done in ShadowCubeApp::OnContextReleased callback method with a helper method ShadowCubeApp::RenderPass::Release() releasing render pass pipeline states:

void ShadowCubeApp::OnContextReleased(gfx::Context& context)
{
    m_final_pass.Release();
    m_shadow_pass.Release();

    m_floor_buffers_ptr.reset();
    m_cube_buffers_ptr.reset();

    m_shadow_sampler = {};
    m_texture_sampler = {};
    m_const_buffer = {};
    m_shadow_pass_pattern = {};

    UserInterfaceApp::OnContextReleased(context);
}

void ShadowCubeApp::RenderPassState::Release()
{
    render_state = {};
    view_state = {};
}

Frame Rendering Cycle

Animation function bound to time-animation in constructor of ShadowCubeApp class is called automatically as a part of every render cycle, just before App::Update function call. This function rotates light position and camera in opposite directions.

ShadowCubeApp::ShadowCubeApp()
{
    ...
    GetAnimations().emplace_back(std::make_shared<Data::TimeAnimation>(std::bind(&ShadowCubeApp::Animate, this, std::placeholders::_1, std::placeholders::_2)));
}

bool ShadowCubeApp::Animate(double, double delta_seconds)
{
    m_view_camera.Rotate(m_view_camera.GetOrientation().up, static_cast<float>(delta_seconds * 360.F / 8.F));
    m_light_camera.Rotate(m_light_camera.GetOrientation().up, static_cast<float>(delta_seconds * 360.F / 4.F));
    return true;
}

ShadowCubeApp::Update() function is called before App::Render() call to update shader uniforms:

Scene uniforms structure is updated with eye and light positions calculated in ShadowCubeApp::Animate function.
Cube and Floor mesh uniform structures are updated separately for Final and Render passes:
- Shadow pass MVP matrix is calculated from the light point of view using m_light_camera.GetViewProjMatrix() and the shadow-MVPx matrix is not used for shadow-map rendering, so it is set to zero matrix.
- Final pass MVP matrix is calculated from the observer point of view using m_view_camera.GetViewProjMatrix(). The shadow-MVPx matrix is used to calculate current pixel coordinates in the shadow-map texture, so we use MVP matrix used during shadow pass rendering multiplied by coordinates transformation matrix to convert from homogenous [-1, 1] to texture coordinates [0,1].

bool ShadowCubeApp::Update()
{
    if (!UserInterfaceApp::Update())
        return false;

    // Prepare homogenous [-1,1] to texture [0,1] coordinates transformation matrix
    static const hlslpp::float4x4 s_homogen_to_texture_coords_matrix = hlslpp::mul(hlslpp::float4x4::scale(0.5F, -0.5F, 1.F), hlslpp::float4x4::translation(0.5F, 0.5F, 0.F));

    // Update scene uniforms
    m_scene_uniforms.eye_position    = hlslpp::float4(m_view_camera.GetOrientation().eye, 1.F);
    m_scene_uniforms.light_position  = m_light_camera.GetOrientation().eye;

    hlslpp::float4x4 scale_matrix = hlslpp::float4x4::scale(m_scene_scale);

    // Cube model matrix
    hlslpp::float4x4 cube_model_matrix = hlslpp::mul(hlslpp::float4x4::translation(0.F, 0.5F, 0.F), scale_matrix); // move up by half of cube model height

    // Update Cube uniforms
    m_cube_buffers_ptr->SetFinalPassUniforms(hlslpp::MeshUniforms{
        hlslpp::transpose(cube_model_matrix),
        hlslpp::transpose(hlslpp::mul(cube_model_matrix, m_view_camera.GetViewProjMatrix())),
        hlslpp::transpose(hlslpp::mul(hlslpp::mul(cube_model_matrix, m_light_camera.GetViewProjMatrix()), s_homogen_to_texture_coords_matrix))
    });
    m_cube_buffers_ptr->SetShadowPassUniforms(hlslpp::MeshUniforms{
        hlslpp::transpose(cube_model_matrix),
        hlslpp::transpose(hlslpp::mul(cube_model_matrix, m_light_camera.GetViewProjMatrix())),
        hlslpp::float4x4()
    });

    // Update Floor uniforms
    m_floor_buffers_ptr->SetFinalPassUniforms(hlslpp::MeshUniforms{
        hlslpp::transpose(scale_matrix),
        hlslpp::transpose(hlslpp::mul(scale_matrix, m_view_camera.GetViewProjMatrix())),
        hlslpp::transpose(hlslpp::mul(hlslpp::mul(scale_matrix, m_light_camera.GetViewProjMatrix()), s_homogen_to_texture_coords_matrix))
    });
    m_floor_buffers_ptr->SetShadowPassUniforms(hlslpp::MeshUniforms{
        hlslpp::transpose(scale_matrix),
        hlslpp::transpose(hlslpp::mul(scale_matrix, m_light_camera.GetViewProjMatrix())),
        hlslpp::float4x4()
    });
    
    return true;
}

Scene rendering consists is done in ShadowCubeApp::Render() method in 4 steps:

5 Volatile uniform buffers are updated with uniform structures data, previously calculated and filled in ShadowCubeApp::Update() method.
Shadow pass rendering commands are encoded with ShadowCubeApp::RenderScene(...) method for the current scene using already configured shadow render pass bound to shadow render command list and shadow-pass uniforms.
Final pass rendering commands are encoded with ShadowCubeApp::RenderScene(...) method for the same scene using already configured final render pass bound to final render command list and final-pass uniforms.
Shadow and Final pass rendering command lists are sent for execution to GPU using render command queue from context and frame present is scheduled.

bool ShadowCubeApp::Render()
{
    if (!UserInterfaceApp::Render())
        return false;

    // Upload uniform buffers to GPU
    const ShadowCubeFrame& frame = GetCurrentFrame();
    const rhi::CommandQueue render_cmd_queue = GetRenderContext().GetRenderCommandKit().GetQueue();
    frame.scene_uniforms_buffer.SetData(render_cmd_queue, m_scene_uniforms_subresource);
    frame.shadow_pass.floor.uniforms_buffer.SetData(render_cmd_queue, m_floor_buffers_ptr->GetShadowPassUniformsSubresources());
    frame.shadow_pass.cube.uniforms_buffer.SetData(render_cmd_queue, m_cube_buffers_ptr->GetShadowPassUniformsSubresources());
    frame.final_pass.floor.uniforms_buffer.SetData(render_cmd_queue, m_floor_buffers_ptr->GetFinalPassUniformsSubresources());
    frame.final_pass.cube.uniforms_buffer.SetData(render_cmd_queue, m_cube_buffers_ptr->GetFinalPassUniformsSubresources());

    // Record commands for shadow & final render passes
    RenderScene(m_shadow_pass, frame.shadow_pass);
    RenderScene(m_final_pass, frame.final_pass);

    // Execute rendering commands and present frame to screen
    GetRenderContext().GetRenderCommandKit().GetQueue().Execute(frame.execute_cmd_list_set);
    GetRenderContext().Present();
    
    return true;
}

Scene rendering commands encoding is done similarly for both shadow and render passes:

Render command list is reset with state taken from render pass resources and already configured debug group description.
View state is set with viewports and scissor rects.
Cube and floor meshes drawing commands are encoded using TexturedMeshBuffers::Draw(...) method which is doing:
1. Setting program bindings to resources;
2. Setting vertex buffer to draw;
3. Encodes DrawIndexed command for a given mesh subset.
4. Methane application overlay is rendered as a part of Final pass only using Graphics::App::RenderOverlay(...) method from base application class.
5. Command list is committed making it ready for execution.

void ShadowCubeApp::RenderScene(const RenderPassState& render_pass, const ShadowCubeFrame::PassResources& render_pass_resources) const
{
    const rhi::RenderCommandList& cmd_list = render_pass_resources.cmd_list;

    // Reset command list with initial rendering state
    cmd_list.ResetWithState(render_pass.render_state, &render_pass.debug_group);
    cmd_list.SetViewState(render_pass.view_state);

    // Draw scene with cube and floor
    m_cube_buffers_ptr->Draw(cmd_list, render_pass_resources.cube.program_bindings);
    m_floor_buffers_ptr->Draw(cmd_list, render_pass_resources.floor.program_bindings);

    if (render_pass.is_final_pass)
    {
        RenderOverlay(cmd_list);
    }

    cmd_list.Commit();
}

Graphics render loop is started from main(...) entry function using GraphicsApp::Run(...) method which is also parsing command line arguments.

int main(int argc, const char* argv[])
{
    return ShadowCubeApp().Run({ argc, argv });
}

Shadow Cube Shaders

HLSL 6 shaders Shaders/ShadowCube.hlsl implement both shadow pass rendering and final pass with phong lighting, texturing and shadow map sampling all in one source file with help of #ifdef ... #endif pre-processor guards. These code blocks are enabled with macro-definitions passed to shader compiler:

ENABLE_TEXTURING macro-definition:
- Adds texcoord vector to VSInput and PSInput argument structures; enables code for passing texture coordinates from vertex to pixel shader with interpolation.
- Adds texture g_texture along with sampler g_texture_sampler and enables code path for its sampling in pixel shader CubePS.
ENABLE_SHADOWS macro-definition:
- Adds shadow_position vector to PSInput arguments structure and enables code path to calculate it in vertex shader CubeVS;
- Adds shadow_mvpx_matrix matrix to MeshUniforms structure of g_mesh_uniforms buffer;
- Adds shadow-map texture g_shadow_map along with shadow-map sampler g_shadow_sampler and enables code path for shadow map sampling in pixel shader CubePS.

#include "ShadowCubeUniforms.h"
#include "..\..\Common\Shaders\Primitives.hlsl"

struct VSInput
{
    float3 position         : POSITION;
    float3 normal           : NORMAL;
#ifdef ENABLE_TEXTURING
    float2 texcoord         : TEXCOORD;
#endif
};

struct PSInput
{
    float4 position         : SV_POSITION;
    float3 world_position   : POSITION0;
    float3 world_normal     : NORMAL;
#ifdef ENABLE_SHADOWS
    float4 shadow_position  : POSITION1;
#endif
#ifdef ENABLE_TEXTURING
    float2 texcoord         : TEXCOORD;
#endif
};

ConstantBuffer<Constants>     g_constants       : register(b1);
ConstantBuffer<SceneUniforms> g_scene_uniforms  : register(b2);
ConstantBuffer<MeshUniforms>  g_mesh_uniforms   : register(b3);

#ifdef ENABLE_SHADOWS
Texture2D    g_shadow_map      : register(t0);
SamplerState g_shadow_sampler  : register(s0);
#endif

#ifdef ENABLE_TEXTURING
Texture2D    g_texture         : register(t1);
SamplerState g_texture_sampler : register(s1);
#endif

PSInput CubeVS(VSInput input)
{
    const float4 position   = float4(input.position, 1.0F);

    PSInput output;
    output.position         = mul(position, g_mesh_uniforms.mvp_matrix);
    output.world_position   = mul(position, g_mesh_uniforms.model_matrix).xyz;
    output.world_normal     = normalize(mul(float4(input.normal, 0.0), g_mesh_uniforms.model_matrix).xyz);
#ifdef ENABLE_SHADOWS
    output.shadow_position  = mul(position, g_mesh_uniforms.shadow_mvpx_matrix);
#endif
#ifdef ENABLE_TEXTURING
    output.texcoord         = input.texcoord;
#endif

    return output;
}

float4 CubePS(PSInput input) : SV_TARGET
{
    const float3 fragment_to_light             = normalize(g_scene_uniforms.light_position - input.world_position);
    const float3 fragment_to_eye               = normalize(g_scene_uniforms.eye_position.xyz - input.world_position);
    const float3 light_reflected_from_fragment = reflect(-fragment_to_light, input.world_normal);

#ifdef ENABLE_SHADOWS
    const float3 light_proj_pos = input.shadow_position.xyz / input.shadow_position.w;
    const float  current_depth  = light_proj_pos.z - 0.0001F;
    const float  shadow_depth   = g_shadow_map.Sample(g_shadow_sampler, light_proj_pos.xy).r;
    const float  shadow_ratio   = current_depth > shadow_depth ? 1.0F : 0.0F;
#else
    const float  shadow_ratio   = 0.F;
#endif

#ifdef ENABLE_TEXTURING
    const float4 texel_color    = g_texture.Sample(g_texture_sampler, input.texcoord);
#else
    const float4 texel_color    = { 0.8F, 0.8F, 0.8F, 1.F };
#endif

    const float4 ambient_color  = texel_color * g_constants.light_ambient_factor;
    const float4 base_color     = texel_color * g_constants.light_color * g_constants.light_power;

    const float  distance       = length(g_scene_uniforms.light_position - input.world_position);
    const float  diffuse_part   = clamp(dot(fragment_to_light, input.world_normal), 0.0, 1.0);
    const float4 diffuse_color  = base_color * diffuse_part / (distance * distance);

    const float  specular_part  = pow(clamp(dot(fragment_to_eye, light_reflected_from_fragment), 0.0, 1.0), g_constants.light_specular_factor);
    const float4 specular_color = base_color * specular_part / (distance * distance);

    return ColorLinearToSrgb(ambient_color + (1.F - shadow_ratio) * (diffuse_color + specular_color));
}

CMake Build Configuration

Shaders are compiled in build time and are added as byte code to the application embedded resources. Note that vertex shader CubeVS is built twice with different set of macro definitions: one instance is used for shadow pass, the other is for final pass rendering. Texture images are added to the application embedded resources too.

include(MethaneApplications)
include(MethaneShaders)
include(MethaneResources)

add_methane_application(
    TARGET MethaneShadowCube
    NAME "Methane Shadow Cube"
    DESCRIPTION "Tutorial demonstrating shadow and final render passes done with Methane Kit."
    INSTALL_DIR "Apps"
    SOURCES
        ShadowCubeApp.h
        ShadowCubeApp.cpp
        Shaders/ShadowCubeUniforms.h
)

set(TEXTURES_DIR ${RESOURCES_DIR}/Textures)
list(APPEND TEXTURES
    ${TEXTURES_DIR}/MethaneBubbles.jpg
    ${TEXTURES_DIR}/MarbleWhite.jpg
)
add_methane_embedded_textures(MethaneShadowCube "${TEXTURES_DIR}" "${TEXTURES}")

add_methane_shaders_source(
    TARGET MethaneShadowCube
    SOURCE Shaders/ShadowCube.hlsl
    VERSION 6_0
    TYPES
        frag=CubePS:ENABLE_SHADOWS,ENABLE_TEXTURING
        vert=CubeVS:ENABLE_SHADOWS,ENABLE_TEXTURING
        vert=CubeVS:ENABLE_TEXTURING
)

add_methane_shaders_library(MethaneShadowCube)

target_link_libraries(MethaneShadowCube
    PRIVATE
    MethaneAppsCommon
)

Continue learning

Continue learning Methane Graphics programming in the next tutorial Typography, which is demonstrating text rendering using dynamic font atlas textures.

MethaneKit

Shadow Cube Tutorial

Application Controls

Application and Frame Class Definitions

Graphics Resources Initialization

Frame Rendering Cycle

Shadow Cube Shaders

CMake Build Configuration

Continue learning

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MethaneKit

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Shadow Cube Tutorial

Application Controls

Application and Frame Class Definitions

Graphics Resources Initialization

Frame Rendering Cycle

Shadow Cube Shaders

CMake Build Configuration

Continue learning

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