Search found 42 matches

by papaboo
Fri Mar 06, 2015 1:25 pm
Forum: General Development
Topic: Defining roughness
Replies: 6
Views: 5255

Defining roughness

Hey I was wondering if there was a definition of roughness for glossy/microfacet BRDFs, as this could be useful to a lot of stuff in one of my renderers. Fx ⋅  An SPPM integrator bases the decision about whether or not to gather photons or continue tracing on the materials roughness. I hav...
by papaboo
Mon Feb 23, 2015 2:59 pm
Forum: General Development
Topic: photon mapping + final gather light leaks
Replies: 2
Views: 3070

Re: photon mapping + final gather light leaks

Photon mapping comes with geometric bias and light leaking. There are various ways to reduce it, but you can't remove it without an infinite number of samples and a really really really high precision backbuffer. That being said you can 'postpone' the light leaking until it's is no longer noticeable...
by papaboo
Sat Oct 25, 2014 6:04 pm
Forum: General Development
Topic: How to render soft shadow from directional light
Replies: 4
Views: 4116

Re: How to render soft shadow from directional light

how to render reflected specular high light from delta light sources like directional lights or point lights Please don't go there. :) A point light has zero radius and cannot be sampled from a specular surface. The probability of a specular ray hitting the exact point at which your pointlight lies...
by papaboo
Fri Aug 22, 2014 6:37 am
Forum: General Development
Topic: questions about hair rendering
Replies: 5
Views: 4431

Re: questions about hair rendering

Disclaimer: I haven't read any of the source code or played around with it, so I don't know how well it works. But! I would take a look at Embree. A lot of their 2.x.y relaese notes are concerned with hair, so clearly the guys have invested time in solving this issue. You might need to tweak their s...
by papaboo
Fri Jun 20, 2014 2:57 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8301

Re: Energy-Conserving Phong Specular Lobe

Disclaimer: In a rush, so only glanced at the code. Hope this is still helpful. 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 insi...
by papaboo
Fri Mar 07, 2014 12:18 pm
Forum: General Development
Topic: SBVH - support of different kind of primitives
Replies: 3
Views: 3791

Re: SBVH - support of different kind of primitives

You write that it's a GPU engine, so separation of primitives might not be a bad idea. It will decrease tree quality, sure, but it will increase coherence among threads in a warp, which can be a lot more critical. My personal preference for a GPU raytracer with support for multiple primitives (tris,...
by papaboo
Thu Feb 27, 2014 8:39 am
Forum: General Development
Topic: Implementing a Shader System
Replies: 13
Views: 10327

Re: Implementing a Shader System

Hey, Welcome to the world of noise and pretty colors :) Physically Based Rendering is a great resource yes. Start there and then go digging for articles on anything you want to know more about. As spectral said, the easiest is to base you material system on layered BSDFs. This allows you to describe...
by papaboo
Wed Feb 12, 2014 12:05 pm
Forum: General Development
Topic: Hair intersection : approaches ?
Replies: 16
Views: 13163

Re: Hair intersection : approaches ?

There's the stochastic transparency approach to transparency.

http://www.nvidia.com/object/nvidia_res ... b_016.html

But if you're targeting real-time rendering I don't know if you want a random element in your renderer which could potentially produce artefacts in certain scenarios.
by papaboo
Sun Feb 09, 2014 7:32 am
Forum: General Development
Topic: CUDA and branch prediction
Replies: 2
Views: 3815

Re: CUDA and branch prediction

I haven't found anything similar too it no. However, branching is mostly performance intensive if some threads in a warp (halfwarp maybe) take divergent paths. So instead of focusing on and optimizing the branch, you might want to look at your overall algorithm and se if you can launch warps that ta...
by papaboo
Tue Aug 06, 2013 8:12 am
Forum: Links & Papers
Topic: Ray Tracing is the Future and ever will be
Replies: 23
Views: 24112

Re: Ray Tracing is the Future and ever will be

I was doing some quick profiling of Optix 3.0 last friday and it does indeed seem to compile into a mega kernel, since all I could find where calls to trace_1. However, I'm currently only compiling for devices of compute capability 1.0 and on such old devices it makes sense to generate a giant kerne...

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