Material for studying 6.3 section of ShaderX5

1. Interactive Refractions and Caustics Using Image-Space Techniques Shader Study (http://cafe.naver.com/shader.cafe) Codevania (http://codevania.blogspot.com)

2. Reflection… Refraction… Caustic…

4. Goal is…

22. Putting it Together

27. Rendering Caustic Map Use photon data in vertex shader, render points at photon locations Light Space Eye Space

30. Examples and Discussion

32. Code snippets RenderCaustics { // create the buffers needed for refraction from light (for caustics) createRefractionBuffers // create all the necessary buffers (normal, bg geom, depth, etc) from a particular POV // draw the normals for the back side createBackSideMaps // Draw just the background geometry createOtherObjectEyeTexture // draw the caustics positions & directions info to the framebuffer DrawSceneCausticsToBuffer // Draw refractive geometry from a particular POV // store positions of final hitpoints into a secondary buffer set the eye's lookat Draw the environment map Draw the refractor Draw the non refractive objects in the scene PerformLightSpaceGather // find caustic contribution using an image-space gather using a image from the light's POV draw photons splats using point sprites } // Now we've got our caustic map. However, simply projecting this onto the // scene means any surface will get a caustic, whether shadowed (from the refractor) or not! // By copying the depth buffer from the background image we used above, // we can sort this out to only cast caustics onto the "frontmost" surface behind the refractor

33. Code snippets DrawCausticsSceneWithLightSpaceGatheredPhotons { if ( needToRerenderCaustics ) RenderCaustics // create the buffers needed for refraction from the "eye's" point of view CreateRefractionBuffersForLightSpacePhotonGather // create all the necessary buffers (normal, bg geom, depth, etc) from a particular POV // Draw just the background geometry (MacBeth, Dragon, etc) DrawShadowedBackgroundWithLightSpaceCaustics DrawEnvironmentMap compute the shadow map matrix index into 'light-space caustic map' displayBackGroundGeometry // draw the normals for the back side createBackSideMaps // draw the scene, with caustics on the background geometry, refracted thru the refractor FinalDrawWithAlreadyComputedLightSpaceGather // takes the background geometry textures // (which includes one with accumulated photon contributions) set the eye's lookat //Draw the (background) non refractive objects in the scene displayLargeTextureWithDepth // Go ahead and actually draw the refractive object glCallList }

34. Graphical Overview (1) Eye-space background image without refractor (2) Eye-space background surface depth map (3) Light-space background surface depth map (4) Eye-space view of refractor's backfacing surface normals (5) Eye-space view of refractor's backfacing surface depth (6) Four frame caustic map (one frame's intensity per channel) (7) Current frame's photon buffer (i.e., the photon positions) (8) Surface normal at final photon positions (light-space) (9) Light-space depth map (a.k.a. the shadow map)