Retrospect Digital Image Synthesis Yu-Ting Wu. So far we have learned: Geometry and transforms...

Retrospect

Digital Image SynthesisYu-Ting Wu

So far we have learned:

• Geometry and transforms• Shapes• Accelerators• Color and radiometry• Cameras• Sampling and reconstruction• Reflection models• Materials• Textures

Recap: the process of renderingCamerasorthogonal, perspective, environment, realistic …

Samplingrandom, stratified, low-discrepancy, best candidate …Reconstructionbox, triangle, sinc, Gaussian, Mitchell …

GenerateRay

Intersect

Shapessphere, disk, cylinder, triangle meshes, subdivision surfaces …

IntersectionDifferentialGeometryBSDFs

Materialsmatte, plastic, mix, measured, metal, substrate …

Lightspoint, distant, spot, area, environment …

Acceleratorsgrid, bvh, kdtree …

)ωp,( ooL )ω,p( oeL

iω 2

ds iiio θcos)ωp,()ω,ωp,( iLf

GetBSDF

Cameras

• GenerateRay– Given a sample on the image film (in raster

space), generate the corresponding camera ray (in world space) according to the type of camera.

environment

Cameras

• Depth-of-field and motion blur

Depth-of-field

Motion blur

Shapes

• Intersect (used for radiance ray)• Given a ray, does it has intersection with the

shape?• If yes, fill the information in

DifferentialGeometry• IntersectP (used for shadow ray)

– Given a ray, does it has intersection with the shape?

IntersectIntersect

IntersectP

scene

Materials, textures and reflectance models• Materials

– GetBSDF

• Reflectance models (BxDFs)– f– Sample_f

• Textures– Evaluate

Material

TextureSpatially-varying

parameters

BxDFsreflectance models

Accelerators

• Construction• Traversal

• Intersect (used for radiance ray)– IntersectP (used for shadow ray)

BVH Uniform grid Octree Kdtree BSP tree

Sampling and reconstruction

• Use sub-pixel samples for– Antialiasing– Distributed effects

• Depth-of-field• Motion blur• Soft shadows• Glossy reflection• Global illumination

Sampling and reconstruction

• Sampling patterns

random stratified uniform stratified jittered

Halton Hammersley best candidate

Call stack in pbrtRenderer::Render RenderTask::Run Camera::Film::WriteImage

RenderTask::Run Camera::GenerateRay Renderer::Li

Renderer::Li Scene::Intersect if there is an intersection SurfaceIntegrator::Li else Light::Le VolumeIntegrator::Li return T * Li + Lvi

[render a block of pixels]

[output an image]

[obtain a camera ray for each camera sample][compute the radiance carried by the camera ray]

[obtain the intersection of the ray and the scene]

[compute the surface reflectance along the ray]

[possibly add emittance from all lights]

[compute volume contribution and transmittance]

Call stack in pbrtScene::Intersect Aggregate::Intersect SurfaceIntegrator::Li Intersection::GetBSDF <Do shading based on the shading geometry and BSDF>

Intersection::GetBSDF Primitive::GetBSDF

Primitive::GetBSDF Shape::GetShadingGeometry Material::GetBSDF

[call acceleration structure for intersection]

[get BSDF for shading]

[call the intersected primitive to fill the BSDF ]

[call shape to get shading geometry]

[do bump mapping if necessary, call material to get BSDF]

Remaining components:

• Lights• Monte Carlo• Surface integrators• Volume integrators



GenerateRay

Intersect






Li

How much radiance reflected from surface? Surface Integrators

GetBSDF



GenerateRay

Intersect



How much radiance absorbed and scattered by the media? Volume Integrators




GetBSDF

Recap: the process of rendering

• Are we close to this beautiful image?

What’s for next?

• Lights• Homework assignment #3• A brief introduction to the Many-Light

rendering

Retrospect Digital Image Synthesis Yu-Ting Wu. So far we have learned: Geometry and transforms...

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