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License: Apache License 2.0

C++ 59.55% GLSL 2.47% C 36.26% Objective-C 1.61% CMake 0.08% Makefile 0.02%

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graphic's Issues

Voxelization takes too long 350ms++

Implementations tasklist

Looping of deferred fragments
Visualization of octree
Octree voxel information storing
- Surface attribute
  - Texture color/Material color represented as an opacity weight color value (alpha pre-multiplied)
  - Normal is also pre-multiplied by opacity value. Store as isotropic Gaussian lobes.
  - material
- Storing lighting information
  - incoming radiance: Render in light view 1024 x 1024 -> world position -> store in octree as direction distribution and an energy proportional to subtended solid angle of the pixel as seen from the light. Store as isotropic Gaussian lobes.
- Model directional information with distributions that describe the underlying data.
  - Gaussian lobes characterized by an average vector D and a standard deviation σ.
  - To ease interpolation variance is encode via the norm |D| such that σ^2 = (1-|D|)/|D|
- Estimate occlusion info in form of visibility % of blocked rays. Single average value. (Lack view-dependency)
Octree border transfer for surface attribute, light
- 6 passes -x +x -y +y -z +z. add, then copy back
Octree level filtering surface attribute, light
- MIP-mapped with guassian weight, center: 1/4, side: 1/8, corner: 1/16
- 3 passes.
  - 1st computes center voxel with filtered 27 voxels a level below
  - 2nd computes half of the filtered response at sides (18 each side)
  - 3rd computes quarter of filtered response at corners (4 each corner)
- border transfer to complete information from other octants
Light filtering considerations. Avoid filtering zero values
- Derive 2D node map form light-view map(MIP-map pyramid)
- Stores indices of 3D leaf nodes containing corresponding photon in light-view map
- 1 thread per pixel per octree mip-mapping pass.
- Uses 2D node map to verify common-ancestor with other thread.
- Terminate all thread except upper left one.
Voxel Cone Tracing
- Step along cone axis and perform lookups in octree at level corresponding to the cone radius
- Quadrilinear interpolation to ensure smooth variation.
- Use emission-absorption optical model to accumulate values along the cone.
- Track occlusion and color representing the reflected light towards cone origin.
- Compute new outgoing radiance with scene filtered information and occlusion.
- Update values with volumetric front-to-back accumulation c = a_c+ (1-a)a2_c2 and a = a + (1-a)a2.
- To ensure good integration quality, the distance d' between successive sample locations along a ray does not coincide with the current voxel size d.
- To account for the smaller step size, use correction a'_s = 1 - (1-a_s)^(d'/d)
Ambient Occlusion
- Weight occlusion a by a function f(r) which decays with distance. (1/(1+λr)). a_f(p+rω):= f(r)a(p+rω_v). v = vector
- Partition hemisphere into sum of integral cones.
- Weighted visibility integral V is obtained by accumulating the occlusion information only accounting for weight f(r). Sum of cones = approximation of AO term.
Two-bounce Indirect Illumination
- Use deferred shading for surface points that need indirect illumination.
- At each location, perform gathering with several VCT. Phong (five large cone for diffuse, a tight cone in reflected direction wrt viewpoint captures specular component.)
- aperture of specular cone is from specular exponent of the material. (Glossy reflections)
For better pre-integration of voxel values, use anisotropic voxel representation when building or updating octree.
FPS/timer tracker
Improved modularity for shaders

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