# Tag Info

Accepted

### Progressive Path Tracing with Explicit Light Sampling

There are multiple areas in path tracing that can be importance sampled. In addition, each of those areas can also use Multiple Importance Sampling, first proposed in Veach and Guibas's 1995 paper. To ...
• 3,792
Accepted

### Difference between BVH and Octree/K-d trees

Well I researched quite a lot after that and this paper helped a lot. "Space Subdivision algorithms" by Macdonald 1988. So just summing what I understood. Some of them are obvious reasons but after ...
• 2,478
Accepted

### Raytracing: why are the spheres in the image below appear stretched?

Shapes appearing stretched in the periphery is a consequence of perspective projection. The wider the field of view (FOV) is, the stronger the stretching effect gets. To demonstrate the effect I ...
• 4,420

### Rendering equation - why unsolvable directly?

I'm sadly not able to add a comment to the answer above (not enough reputation), so I will do it like this. I'd like to point out that what Dragonseel describes is simply an integral equation (...
• 304

### Path tracing the Cook-Torrance BRDF

I am posting this for anyone wondering about the confusion between the terms $\frac{1}{\pi}$ and $\frac{1}{4}$. The term $\frac{1}{\pi}$ is an error from the original Cook-Torrance reference. In ...
• 546

### How is Anti Aliasing Implemented in Ray Tracing?

Raxvan is completely right that "traditional" anti aliasing techniques will work in raytracing, including those that use information such as depth to do antialiasing. You could even do temporal anti ...
• 7,801

### Rendering equation - why unsolvable directly?

The rendering equation is as follows: Now, the integral is over the sphere around the point $x$. You integrate over some attenuated light, incoming from every direction. But how much light comes in? ...
• 1,810
Accepted

### How is Anti Aliasing Implemented in Ray Tracing?

I think it's safe to say that there are two different ways of doing AA in raytracing: 1: if you have the final image and the depth image it is possible to apply almost all existing techniques that ...
• 253
Accepted

### A recent approach for subsurface scattering

As mentioned in the comments, I would highly suggest starting with Full Volumetric Scattering. This is two fold: Since you are doing path tracing, adding volumetrics isn't super difficult. Fully ...
• 3,792
Accepted

### Path tracing the Cook-Torrance BRDF

According to this paper, the $\frac{1}{\pi}$ in your $f_r$ should be $\frac{1}{4}$: $$f_r = \frac{DFG}{4(n\cdot w_i)(n \cdot w_o)},$$ so you would end up with  \frac{\pi}{2}L_i(p,w_k)\left(\frac{...
• 302
Accepted

### Mirror Reflections: Ray Tracing or Rasterisation?

There are a couple of special cases where mirror-like reflections can be rendered efficiently using rasterization techniques, and these are commonly used in games, although they don't work for the ...
• 25.1k
Accepted

### Does cosine weighted hemisphere sampling still require NdotL when calculating contribution for indirect light?

You always need to multiply by the cosine term indeed (that's part of the rendering equation). Though when you do indirect diffuse using ray-tracing and thus monte-carol integration (which is the most ...
• 656
Accepted

### How am I able to perform perspective projection without a near plane?

The near and far planes of a viewing frustum aren't needed for simple 3D→2D projection. What the near and far planes actually do, in a typical rasterizer setup, is define the range of values for the ...
• 25.1k
Accepted

### What effects does path tracing capture that recursive ray tracing does not?

Generally speaking, path tracing removes a number of assumptions that ray tracing makes. Ray tracing usually assumes that there is no indirect lighting (or that indirect lighting can be approximated ...
• 4,012
Accepted

### Non Real Time Raytracing

Path tracing is the standard technique in non-realtime photorealistic rendering, and you should look specifically into bidirectional path tracing to get effects like caustics, which you can't really ...
• 3,646

### How to raytrace Bezier surfaces?

is it a total pipe dream to hope to solve the Ray/Bezier-surface intersection algebraically Yes, it's a pipe dream. A bicubic Bezier patch is an algebraic surface of degree 18. To intersect a ray ...
• 348

### Why does the 1/r² term appear with point sources?

The concept of a point source is an approximation. Physically, light sources are extended objects and emit light from every point on their surface; but when you're far enough away (i.e. the distance ...
• 25.1k
Accepted

### Ray casting in fan configuration produces point cloud with curvature, how to eliminate curvature?

The direction vectors start at +15 degrees on the YZ plane, and continue in increments of -2 degrees down to -15. There's your problem—by generating the rays that way, you're doing something more ...
• 25.1k
Accepted

### Area Lights in Path Tracing

I'm going to provide the simple/naive/brute force answer to this question, which does work, and gives accurate results. There are better answers however, which make the rendering converge faster with ...
• 7,801
Accepted

### Should ideal specular multiply light colour with material colour?

What "ideal" means in this context is that there is no divergence in the direction of light reflection vectors (i.e. no roughness) but that they are all considered to be perfect reflections from an ...
• 3,646
Accepted

The shadow terminator problem (as it's also known) is still something of an open problem in ray-tracing. As you say, disabling self-shadowing is not a very good workaround, because non-convex meshes ...
• 6,840
Accepted

### Subsurface Scattering Without Rays?

There are lots of ways to fake SSS with greater or lesser fidelity. A few recent-ish methods: Screen-space blurring of object lighting (described in detail here) Using “interior” ambient-occlusion ...
• 2,222
Accepted

### Can a glass plate act like a lens?

The box.obj file has no vertex normals, and by default Mitsuba will generate smooth normals for OBJ files that don't specify their own normals. This creates the ...
• 25.1k

### Grainy image in my simple ray tracer

It's likely due to shadow rays. When the light source is exactly on the plane of the wall, a shadow ray traced to it may or may not be found to intersect the wall before it reaches the light. The ...
• 25.1k
Accepted

### Should direct illumination and path tracers render the same scene equally bright?

The results that you are getting, are not correct. More specifically, your direct illumination ray tracer is not correct. When limiting a path tracer's bounces to only allow for any direct ...
• 1,605

### Fundamental drawbacks of rasterization over ray tracing

Rasterization is based on the idea of projecting various primitives (e.g. triangles, line segments, points, quads, maybe even some curved surfaces like bezier patches) on the screen and then ...
• 2,226

### Is there a method to do ray marching style modulus repeat with raytracing?

I've tried to figure this out as well, but I don't think there is a solution that is just as performant as tracing one sphere. Basically you would want to cast one ray to hit a infinite set of ...