Search found 29 matches

by Geometrian
Mon Jul 07, 2014 5:44 am
Forum: General Development
Topic: Camera Weighting in Eye Tracing
Replies: 10
Views: 8444

Re: Camera Weighting in Eye Tracing

Yes . . . but how is the proper weighting computed? Look at SmallPT. It does not model depth-of-field, which means it is a pinhole camera. Since you can see anything at all, it has an infinite exposure time--for a very fuzzily defined notion of "infinite". If you were to increase the aperture at all...
by Geometrian
Sat Jul 05, 2014 3:32 am
Forum: General Development
Topic: Camera Weighting in Eye Tracing
Replies: 10
Views: 8444

Camera Weighting in Eye Tracing

Hi, In real life the aperture size (and exposure time) affect how bright the image is. This happens because a larger aperture means more light paths hit the sensor, and a longer exposure time integrates more energy. How is this implemented in a unidirectional eye tracer (trace rays from camera until...
by Geometrian
Thu Jun 26, 2014 9:35 pm
Forum: General Development
Topic: Sampling Distorted Spheres
Replies: 4
Views: 3977

Re: Sampling Distorted Spheres

I don't know if this is the correct way to do it, but what I've been doing in Psychopath is sampling in the local space of the sphere, and then transforming the resulting vector into world space after the fact. I can imagine this may be incorrect, though, since for non-uniform scaling, shearing, et...
by Geometrian
Wed Jun 25, 2014 4:18 pm
Forum: General Development
Topic: Sampling Distorted Spheres
Replies: 4
Views: 3977

Sampling Distorted Spheres

I can generate a ray on the surface of a hemisphere pointing toward a random location on a distant sphere fairly simply: you sample over a circle on the surface of the hemisphere corresponding to the projected sphere. The sampling itself can be achieved by e.g. this . However, if the sphere is trans...
by Geometrian
Tue Jun 24, 2014 11:29 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8538

Re: Energy-Conserving Phong Specular Lobe

You are using a hemispherical source so the reflected radiance should never go higher than 0.5. But it can go lower. The Phong lobe is oriented around the reflection vector. So the reflection hemisphere is not oriented around the surface normal. In other words, the reflection sampling hemisphere is...
by Geometrian
Mon Jun 23, 2014 7:09 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8538

Re: Energy-Conserving Phong Specular Lobe

The microfacet model is generally not energy conserving, which I personally see as a feature, not a drawback. The idea is that rays that reflect of your surface and are reflected into the material will bounce around inside the material forever and never escape (or if it does the contribution is so ...
by Geometrian
Mon Jun 23, 2014 6:56 pm
Forum: General Development
Topic: When do Fresnel Equations Apply/Fresnel BRDFs
Replies: 8
Views: 5615

When do Fresnel Equations Apply/Fresnel BRDFs

As I understand it, when light hits a surface, the Fresnel equations apply. These equations depend on the complex-valued refractive index of the material, which itself depends on the incident light's wavelength. However, for purely-diffuse surfaces, the results are also generally bad. Paper, wood, a...
by Geometrian
Fri Jun 20, 2014 12:25 am
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8538

Re: Energy-Conserving Phong Specular Lobe

As I understand it, PDFs are the probability density associated with choosing a ray; they correspond directly to the method of sampling. BRDFs define a proportion of light reflected. I think I've got that pretty well. I redid everything more carefully and have arrived at the following: Vec3 R = get_...
by Geometrian
Wed Jun 18, 2014 7:48 pm
Forum: ompf2
Topic: Latex formula support ?
Replies: 17
Views: 34677

Re: Latex formula support ?

Is this broken again?
by Geometrian
Wed Jun 18, 2014 7:47 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8538

Re: Energy-Conserving Phong Specular Lobe

This one ? I took a quick look just now, and there seems to be some semi-promising things. My progress so far has been to take the Monte Carlo expression of the rendering equation: L'=\int_\Omega L f_r(N\cdot\omega_i)d\omega_i=E\left[\frac{L f_r(N\cdot\omega_i)}{pdf(\omega_i)}\right] Under the ener...