## Search found 7 matches

Tue Mar 04, 2014 10:16 pm
Forum: General Development
Topic: Curve bounding box - fast computation
Replies: 7
Views: 5003

### Re: Curve bounding box - fast computation

I tried this optimization in my renderer. On a scene with thousands of curves, it decreased the rendering times by 10%. Thanks !!
Wed Feb 26, 2014 4:47 pm
Forum: General Development
Topic: Curve bounding box - fast computation
Replies: 7
Views: 5003

### Re: Curve bounding box - fast computation

Quite simply // The transformation matrix you need - Matrix4 is a 4x4 matrix Matrix4 fromCatmullRom = Matrix4( -1, 3, -3, 1, 3, -6, 3, 0, -3, 3, 0, 0, 1, 0, 0, 0 ).inverse() // to bezier space * Matrix4( -1, 3, -3, 1, 2, -5, 4, -1, -1, 0, 1, 0, 0, 2, 0, 0 ) / 2; // from catmull-rom space For each co...
Wed Feb 26, 2014 4:13 pm
Forum: General Development
Topic: Curve bounding box - fast computation
Replies: 7
Views: 5003

### Re: Curve bounding box - fast computation

If you change the basis of your curve from Catmull-Rom to Bezier, the curve is contained into the convex hull of the new control points (this is a property of Bezier curves; this is also true for Bezier surfaces). The bounding box you need is then simply built from the list of control points.
Fri Feb 14, 2014 10:07 pm
Forum: General Development
Topic: Hair intersection : approaches ?
Replies: 16
Views: 13212

### Re: Hair intersection : approaches ?

I suggest that you look at RAY TRACING FOR CURVES PRIMITIVE from Koji Nakamaru & Yoshio Ohno. It comes with detailed pseudo code. I implemented their algoritm into my own renderer and it does the job. You could also take a look at the Embree renderer . Intel folks are currently implementing hair ren...
Sun Dec 30, 2012 6:41 pm
Forum: Visuals, Tools, Demos & Sources
Topic: XRT 2.0 released
Replies: 0
Views: 4176

### XRT 2.0 released

Hi everyone, just a few words to let you know that version 2.0 of my renderer XRT is out. XRT is a multi-threaded raytracing system which implements the RenderMan shading language and the Gelato API (from the now defunct Larry Gritz's Gelato renderer). To get a fair idea of its capabilities, you can...
Sat Mar 17, 2012 8:52 am
Forum: General Development
Topic: Shading model for BART scenes
Replies: 2
Views: 3772

### Re: Shading model for BART scenes

Here is the shader I use for rendering BART scenes (in RenderMan Shading Language) surface aff (color ambientcolor = 0.1; color specularcolor = 0; float roughness = .1; float transmitted = 0.; float index = 1.0; string texturename = ""; ) { normal Nn = faceforward (normalize(N),I); normal In = norma...
Wed Feb 22, 2012 12:24 pm
Forum: General Development
Topic: Total SAH of a BVH
Replies: 11
Views: 11315

### Re: Total SAH of a BVH

There is an example of doing that in the Embree source code