Homework 3 - Transformations, Instancing, Distribution Ray Tracing

In the third assignment of CENG795, we are expected to introduce many new features to the ray tracer, such as:

•  Transformations
•  Instancing
•  Smooth shading
•  Distribution Ray Tracing
• Depth of field
• Soft shadows (area lights)
• Glossy reflections
• Motion blur
• Simple Camera(Constructed with fov, distance, and aspect ratio)
• PLY parsing

Transformations and Instancing:

First I implemented basic transformation classes and matrix operations. If a mesh instance, a sphere, or a primitive triangle has some transformations, I apply them to their bounding boxes for keeping the order of the bvh. For instancing, I separated mesh triangles and primitive triangles. 

• Primitive triangles and spheres convert the ray into their local space to check if it intersects. 
• Mesh instances converts the ray into local space of the their meshes to check if it intersects.
• Meshes and mesh triangles doesn't apply any transformation, they expect rays from their space.
• If an intersection is found after applying transformations, normal is transformed with inverse transpose of the transformation matrix.
• As default, all the meshes has a mesh instance, to keep the code homogeneous.

Smooth shading:

For smooth shading, I needed to calculate vertex normals for every vertex. To do it in linear time, I implemented a vertex class. While processing faces of the meshes, I add the normal of the triangle scaled by the surface area to the vertex normal(for the corner vertices of the triangle). After all calculations are done, I normalize the vertex normal. The reason of scaling is assigning proper weights to the different triangles.

Transformation, instancing and smooth shading
horse_instanced_flat, and horse_instanced_smooth scenes adapted from CENG477 HW2 scene horse_instanced.xml:

  horse_instanced_flat.xml 100 samples 

horse_instanced_smooth.xml 100 samples

killeroo_glass.xml 16 samples

Depth of field:

When a focal length and aperture size is given, I choose a random origin resides in aperture box for the ray. To calculate ray direction, I use samples from the image's focal plane instead of the near plane. I calculate focal plane by using triangle similarity. It causes blur for the objects further and nearer.

spheres_dof.xml 100 samples

Soft shadows:

To achieve rendering soft shadows, I implemented rectangle area lights. Instead of using a constant point of the light as position, I randomly sampled the surface of the light. It causes softer transitions.

Glossy reflections:

To render materials which are imperfected reflectors, I implemented glossy reflections. To achieve this, I randomly perturb the reflection rays according to material's properties.

Soft shadows and glossy reflections:

 metal_plates_point.xml 36 samples

metal_plates_area.xml 36 samples

metal_plates_area.xml 900 samples

Motion blur:

For the real cameras, there is a shutter speed factor. It causes blur on the movement direction for the moving objects. To simulate that behaviour, I picked a random time point for the each sample. For each ray tree, I use its time point to determine positions of the moving objects. Rendering more samples causes less noise on the image.

In this scene point light used instead of area light, <MotionBlur>-5 0 0</MotionBlur> is assigned to the sphere, used reflector material of the cornellbox_dynamic scene(no glossy reflection).

 metal_plates_dynamic.xml 900 samples

cornelbox_dynamic.xml 900 samples

cornellbox_boxes_dynamic.xml 900 samples

dragon_dynamic.xml 100 samples

PLY Parsing:

For ply parsing, I used tinyply. There is one simple proplem about tinyply. Tinyply doesn't support hybrid meshes uses both triangles and quads. I may change the parser in the future. I parse:

• Vertices
• Vertex Normals(if given)
• Face Normals(if given)

Miscellaneous:

Specifications and Benchmarking:

For this assignment, I prepared a cmake project for crossplatform building. I rendered scenes on a different computer.

CPU: ​Intel Core i7-6700 CPU @ 3.40GHz (4 Cores) 

RAM:​ 16 GB 

Operating System:​ Windows 10 64-bi

Platform Toolset: ​Visual Studio 2017 (v141) 

Configurations: ​Release x64

All of them are rendered on #8 threads.

killeroo_glass.xml 16 samples

killeroo_glass.png(800x800) is saved in: 29 seconds 994 milliseconds 245 microseconds

horse_instanced_flat.xml 100 samples

horse_instanced_flat.png(800x400) is saved in: 20 seconds 668 milliseconds 636 microseconds

horse_instanced_smooth.xml 100 samples

horse_instanced_smooth.png(800x400) is saved in: 21 seconds 47 milliseconds 577 microseconds

spheres_dof.xml 100 samples

spheres_dof.png(800x800) is saved in: 11 seconds 2 milliseconds 338 microseconds

cornellbox_dynamic.xml 900 samples

cornellbox_dynamic.png(800x800) is saved in: 3 minutes 21 seconds 2 milliseconds 74 microseconds

cornellbox_boxes_dynamic.xml 900 samples

cornellbox_boxes_dynamic.png(750x600) is saved in: 2 minutes 7 seconds 804 milliseconds 240 microseconds

metal_plates_point.xml 36 samples

metal_plates_point.png(800x800) is saved in: 19 seconds 624 milliseconds 849 microseconds

metal_plates_area.xml 36 samples

metal_plates_area.png(800x800) is saved in: 1 minute 6 seconds 643 milliseconds 764 microseconds

metal_plates_dynamic.xml 900 samples (no roughness)

metal_plates_dynamic.png(800x800) is saved in: 6 minutes 21 seconds 213 milliseconds 532 microseconds

dragon_dynamic.xml 100 samples, max recursion depth 6

dragon_dynamic.png(800x480) is saved in: 4 minutes 24 seconds 183 milliseconds 971 microseconds