Purpose of the Sample:
Demonstrates how to create a framebuffer object and use the color buffer attached to the frame buffer object as input into a full-screen post-processing effect. This example builds on the Stencil Buffer Effect tutorial.
CGame.h
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#ifndef __CGAME__ #define __CGAME__ #include <glad/glad.h> #include "shader_s.h" class Model; class Mesh; class CGame { public: CGame() {}; void Initialize(unsigned int screenWidth, unsigned int screenHeight); void Shutdown(); void Render(); void OnResize(int screenWidth, int screenHeight); private: void SetupGPUProgram(); void SetupModel(); void SetupFullscreenQuad(); Shader* m_pShaderPass0; Shader* m_pShaderPass1; Shader* m_pShaderStencilPass; Shader* m_pShaderBlitPass; Model* m_pManModel; Model* m_pStencilModel; GLuint m_ColorTextureId; GLuint m_IntermediateFBOId; Mesh* m_pFullscreenQuad; unsigned int m_Width; unsigned int m_Height; }; #endif |
CGame.cpp
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#include "CGame.h" #define STB_IMAGE_IMPLEMENTATION #include "stb_image/stb_image.h" #include "Model.h" #include "Mesh.h" #include "glm/mat4x4.hpp" #include "glm/vec3.hpp" #include "glm/glm.hpp" #include "glm/gtc/matrix_transform.hpp" #include "glm/gtc/type_ptr.hpp" #include void CGame::Initialize(unsigned int screenWidth, unsigned int screenHeight) { m_Width = screenWidth; m_Height = screenHeight; SetupGPUProgram(); SetupModel(); SetupFullscreenQuad(); glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LEQUAL); glEnable(GL_STENCIL_TEST); GLuint depthStencilId; glGenFramebuffers(1, &m_IntermediateFBOId); glBindFramebuffer(GL_FRAMEBUFFER, m_IntermediateFBOId); glGenTextures(1, &m_ColorTextureId); glBindTexture(GL_TEXTURE_2D, m_ColorTextureId); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, screenWidth, screenHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_ColorTextureId, 0); glGenRenderbuffers(1, &depthStencilId); glBindRenderbuffer(GL_RENDERBUFFER, depthStencilId); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, screenWidth, screenHeight); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthStencilId); if (glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE) { // Great! } glBindFramebuffer(GL_FRAMEBUFFER, 0); } void CGame::Shutdown() { } void CGame::OnResize(int width, int height) { m_Width = width; m_Height = height; glViewport(0, 0, m_Width, m_Height); glScissor(0, 0, m_Width, m_Height); } void CGame::Render() { static auto startTime = std::chrono::high_resolution_clock::now(); auto currentTime = std::chrono::high_resolution_clock::now(); float time = std::chrono::duration<float, std::chrono::seconds::period>(currentTime - startTime).count(); glBindFramebuffer(GL_FRAMEBUFFER, m_IntermediateFBOId); glEnable(GL_STENCIL_TEST); glClearColor(0.2f, 0.2f, 0.2f, 1.0f); glClearDepth(1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); glColorMask(1, 1, 1, 1); // Draw the Filled Man glEnable(GL_STENCIL_TEST); glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); glStencilFunc(GL_ALWAYS, 0, 0xFF); // all fragments should update the stencil buffer glStencilMask(0xFF); // enable writing to the stencil buffer glm::mat4 model = glm::rotate(glm::mat4(1.0f), time * glm::radians(90.0f), glm::vec3(0.0f, 1.0f, 0.0f)); glm::mat4 view; view = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, -2.0f, -8.0f)); glm::mat4 projection; projection = glm::perspective(glm::radians(60.0f), m_Width / static_cast(m_Height), 0.03f, 100.0f); glm::mat4 mvp = projection * view * model; m_pShaderPass0->use(); m_pShaderPass0->setMatrix4x4("modelMatrix", glm::value_ptr(model)); m_pShaderPass0->setMatrix4x4("viewMatrix", glm::value_ptr(view)); m_pShaderPass0->setMatrix4x4("projectionMatrix", glm::value_ptr(projection)); m_pShaderPass0->setMatrix4x4("mvpMatrix", glm::value_ptr(mvp)); m_pShaderPass0->setFloat("time", time); glDepthFunc(GL_LEQUAL); glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); m_pManModel->meshes[0].Draw(*m_pShaderPass0); // Draw the Stencil Quad glStencilMask(0xFF); model = glm::rotate(glm::mat4(1.0f), glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f)); model = glm::translate(model, glm::vec3(0.0f, 4.0f, -2.5f)); model = glm::scale(model, glm::vec3(1.0f, 1.0f, 1.0f)); mvp = projection * view * model; m_pShaderStencilPass->use(); m_pShaderStencilPass->setFloat("time", time); m_pShaderStencilPass->setMatrix4x4("mvpMatrix", glm::value_ptr(mvp)); glDepthFunc(GL_ALWAYS); glDepthMask(0); glStencilFunc(GL_ALWAYS, 1, 0xFF); glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); glColorMask(0, 0, 0, 0); m_pStencilModel->meshes[0].Draw(*m_pShaderStencilPass); glDepthFunc(GL_LEQUAL); glDepthMask(1); glColorMask(1, 1, 1, 1); // Draw the Wireframe man model = glm::rotate(glm::mat4(1.0f), time * glm::radians(90.0f), glm::vec3(0.0f, 1.0f, 0.0f)); view = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, -2.0f, -8.0f)); projection = glm::perspective(glm::radians(60.0f), m_Width / static_cast(m_Height), 0.03f, 100.0f); mvp = projection * view * model; m_pShaderPass1->use(); m_pShaderPass1->setMatrix4x4("modelMatrix", glm::value_ptr(model)); m_pShaderPass1->setMatrix4x4("viewMatrix", glm::value_ptr(view)); m_pShaderPass1->setMatrix4x4("projectionMatrix", glm::value_ptr(projection)); m_pShaderPass1->setMatrix4x4("mvpMatrix", glm::value_ptr(mvp)); m_pShaderPass1->setFloat("time", time); glStencilFunc(GL_EQUAL, 1, 0xFF); glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); m_pManModel->meshes[0].Draw(*m_pShaderPass1); // Blit intermediate FBO to backbuffer FBO glBindFramebuffer(GL_FRAMEBUFFER, 0); m_pShaderBlitPass->use(); glActiveTexture(0); glBindTexture(GL_TEXTURE_2D, m_ColorTextureId); glDisable(GL_STENCIL_TEST); glDepthFunc(GL_ALWAYS); glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); m_pShaderBlitPass->setFloat("time", time); m_pFullscreenQuad->Draw(*m_pShaderBlitPass); } void CGame::SetupModel() { m_pManModel = new Model(); m_pManModel->Load("man.obj"); m_pStencilModel = new Model(); m_pStencilModel->Load("quad.obj"); } void CGame::SetupGPUProgram() { m_pShaderPass0 = new Shader("vertexPass0.glsl", "fragmentPass0.glsl"); m_pShaderPass1 = new Shader("vertexPass1.glsl", "fragmentPass1.glsl"); m_pShaderStencilPass = new Shader("vertexStencil.glsl", "fragmentStencil.glsl"); m_pShaderBlitPass = new Shader("vertexBlit.glsl", "fragmentBlit.glsl"); } void CGame::SetupFullscreenQuad() { vector vertices; float positions[4][3] = { {-1, -1, 0.3f}, { -1, 1, 0.3f }, { 1, 1, 0.3f }, { 1, -1, 0.3f } }; float uvs[4][2] = { {0,0}, {0,1}, {1,1}, {1,0} }; float indicesVals[6] = { 0,1,2, 0,2,3 }; for (int i = 0; i < 4; ++i) { Vertex vertex; vertex.Position.x = positions[i][0]; vertex.Position.y = positions[i][1]; vertex.Position.z = positions[i][2]; vertex.TexCoords.x = uvs[i][0]; vertex.TexCoords.y = uvs[i][1]; vertices.push_back(vertex); } vector indices(indicesVals, indicesVals + 6); m_pFullscreenQuad = new Mesh(vertices, indices); } |
vertexPass0.glsl – Draw the Filled Man
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#version 330 core layout (location = 0) in vec3 position; layout (location = 1) in vec3 normal; uniform mat4 modelMatrix; uniform mat4 viewMatrix; uniform mat4 projectionMatrix; uniform mat4 mvpMatrix; uniform float time; out vec4 fsNormal; void main() { vec4 pos = mvpMatrix * vec4(position.xyz, 1); fsNormal = vec4(normal.xyz, 0); gl_Position = pos; } |
fragmentPass0.glsl – Shade the Filled Man with his Normals
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#version 330 core out vec4 FragColor; in vec4 fsNormal; void main() { vec3 color = vec3(1,0,0); FragColor = vec4(fsNormal.rgb, 1.0f); } |
vertexStencil.glsl – Render the Quad Mask
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#version 330 core layout (location = 0) in vec3 position; uniform float time; uniform mat4 mvpMatrix; out vec4 fsNormal; void main() { vec3 newModelPos = position + vec3(0, 0, sin(time * 0.4) * 3.0); vec4 pos = mvpMatrix * vec4(newModelPos, 1); gl_Position = pos; } |
fragmentStencil.glsl – Render the Quad Mask
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#version 330 core out vec4 FragColor; void main() { FragColor = vec4(0f, 0f, 0f, 1f); } |
vertexPass1.glsl – Render the Wireframe Man
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#version 330 core layout (location = 0) in vec3 position; layout (location = 1) in vec3 normal; uniform mat4 modelMatrix; uniform mat4 viewMatrix; uniform mat4 projectionMatrix; uniform mat4 mvpMatrix; uniform float time; out vec4 fsNormal; void main() { vec4 pos = mvpMatrix * vec4(position.xyz, 1); fsNormal = vec4(normal.xyz, 0); gl_Position = pos; } |
fragmentPass1.glsl – Render the Wireframe Man
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#version 330 core out vec4 FragColor; in vec4 fsNormal; void main() { vec3 color = vec3(0,1,0); FragColor = vec4(color.rgb, 1.0f); } |
vertexBlit.glsl – Wavy FullScreen Post Processing Effect
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#version 330 core layout (location = 0) in vec3 position; layout (location = 1) in vec3 normal; layout (location = 2) in vec2 uv; uniform float time; out vec2 fsUV; out float fsTime; void main() { fsUV = uv; fsTime = time; gl_Position = vec4(position.xyz, 1); } |
fragmentBlit.glsl – Wavy FullScreen Post Processing Effect
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#version 330 core out vec4 FragColor; in vec2 fsUV; in float fsTime; uniform sampler2D colorBufferTexture; void main() { vec2 uv = fsUV + vec2(sin((fsTime + fsUV.y) * 4.0) * 0.2, 0); vec3 color = texture(colorBufferTexture, uv).rgb; FragColor = vec4(color.rgb, 1.0f); } |
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