Deferred Shading Rasmus Vahtra, Andres Traks Forward rendering - PowerPoint PPT Presentation

Deferred Shading Rasmus Vahtra, Andres Traks

Forward rendering (non-deferred shading)

Forward rendering (non-deferred shading)

Forward rendering (non-deferred shading)

Forward rendering (non-deferred shading) Depth culling

Forward rendering (non-deferred shading)

Forward shader: Vertex Shader (VS) VS PS

Forward shader: Pixel Shader (PS) VS PS

Complexity of forward rendering For each light: For each object: Render() Blend results together

Deferred shading Shading done in a separate rendering pass Pass 1: Render object data into buffers Pass 2: Do lighting/shading VS VS PS PS

Deferred shading: 1) collect data into intermediate textures

Deferred shading: 1) collect data into intermediate textures

Deferred shading: 1) collect data into intermediate textures Depth culling

Deferred shading: 1) collect data into intermediate textures, done Don’t care about geometry anymore

Deferred shader: Vertex Shader (pass 1) VS PS

Deferred shader: Pixel Shader (pass 1) VS PS

Deferred shading: 1) collect data into intermediate textures, done

Deferred shading: 2) Draw a full-screen quad UV = (0, 0) (1, 0) (0, 1) (1, 1)

Deferred shader: Pixel Shader (pass 2)

Review VS PS Forward rendering: Deferred shading: VS VS PS PS

Complexity of deferred rendering For each object: Render geometry data Then shade each pixel on screen exactly once

Deferred shading: VS Pass 2) Draw a full-screen quad VS PS ID TexCoord Position 0 (0, 0) (-1, 1, 0, 1) 1 (1, 0) (1, 1, 0, 1) 2 (0, 1) (-1, -1, 0, 1) 3 (1, 1) (1, -1, 0, 1)

Full screen triangle UV = (1, 0) (2, 0) (0, 0) (0, 1) (1, 1) A bit faster than a quad (0, 2)

G-buffer R G B A Diffuse RGB - Normal XYZ - Depth (32-bit) • 1920 x 1080 x 3 x 32 bits = 24 MB

G-buffer: extra attributes Battlefield 3 Killzone 2

Packing normals 𝑜. 𝑦 2 + 𝑜. 𝑧 2 + 𝑜. 𝑨 2 = 1 Works only with normalized view-space normals! http://aras-p.info/texts/CompactNormalStorage.html

Anti-aliasing Edge-detect Blur if edge detected http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter09.html

Transparent objects? Render them after the deferred pass using forward shading

Deferred lighting

Modifying the G-buffer for deferred lighting R G B A Diffuse RGB - Normal XYZ - Depth (32-bit) Light Accumulation RGB -

Deferred lighting: G-Buffer

Light Stencil Volumes Each point light area is bounded by a sphere (approximate)

Light Stencil Volumes Each point light area is bounded by a sphere (approximate)

Light Stencil Volumes Each point light area is bounded by a sphere (approximate)

Stencil shapes of lights Sphere Cone Fullscreen quad Fullscreen quad http://www.okino.com/new/toolkit/1-14.htm

Other effects: Screen Space Ambient Occlusion (SSAO) http://john-chapman-graphics.blogspot.co.uk/2013/01/ssao-tutorial.html