graphic phrases 4 gbuffer and deferred shading

[ytgui]

https://learnopengl-cn.readthedocs.io/zh/latest/05%20Advanced%20Lighting/08%20Deferred%20Shading/

[ytgui]

Deferred shading

• a screen-space shading technique.

• no shading is actually performed in the first pass of the vertex and pixel shaders: instead shading is "deferred" until a second pass.

• reduce fragment counts

• Forward

  for object in world:
  for vert in object:
      frag = rasterize(vert, texture, normal, light, shadow)
      framebuffer = blend(frame, frag)

• Deferred

  for object in world:
  for vert in object:
      GBuffer += vert, depth, ...
  GBuffer = backface_culling(GBuffer)
  for vert in GBuffer:
  frag = rasterize(vert, texture, normal, light, shadow)
  framebuffer = blend(frame, frag)

• Diffuse Color G-Buffer

• Z-Buffer

• Surface Normal G-Buffer

• Final Compositing.

  (To calculate the shadows shown in this image, other techniques such as shadow mapping, shadow feelers or a shadow volume must be used together with deferred shading.)

[ytgui]

https://learnopengl.com/code_viewer_gh.php?code=src/5.advanced_lighting/8.1.deferred_shading/deferred_shading.cpp

Geometry Pass

// VS
out vec4 gl_Position;
out vec3 FragPos;
out vec2 TexCoords;
out vec3 Normal;

// FS
layout (location = 0) out vec3 gPosition;
layout (location = 1) out vec3 gNormal;
layout (location = 2) out vec4 gAlbedoSpecular;

Lighting Pass

// VS
out vec4 gl_Position;
out vec2 TexCoords;

// FS
void main() {
    // retrieve data from gbuffer
    vec3 FragPos = texture(gPosition, TexCoords).rgb;
    vec3 Normal = texture(gNormal, TexCoords).rgb;
    vec3 Diffuse = texture(gAlbedoSpecular, TexCoords).rgb;
    float Specular = texture(gAlbedoSpecular, TexCoords).a;
}

[ytgui]

MRT in driver

https://gamedev.stackexchange.com/questions/18503/why-would-you-want-multiple-render-targets https://github.com/SaschaWillems/Vulkan/blob/master/examples/deferred/deferred.cpp https://github.com/SaschaWillems/Vulkan