Toxiclibs lighting

ventai

in Contributed Library Questions • 2 years ago

Hi!

I've been playing around with lighting in Toxiclibs, but am getting some low performance with the lighting of faces. Looking at the example below; the faces don't seem to be being lit smoothly as the cube moves. Is this something to do with the normals of the faces? I couldn't quite work out how to 'update' them (as you can see in the below (adapted from code by velvetkevorkian)).
Can anyone please advise as to how this may be possible?

import processing.opengl.*;

import toxi.geom.*;
import toxi.geom.mesh.subdiv.*;
import toxi.geom.mesh.*;
import toxi.processing.*;

ToxiclibsSupport tox;

float rotx,roty= PI/4;

WETriangleMesh mesh;

void setup() {
size(700, 700, OPENGL);
tox= new ToxiclibsSupport(this);
buildMesh();
mesh.computeVertexNormals();
}

void draw() {

translate(width/2,height/2,0);
background(255);
fill(255,0,0);
strokeWeight(0.5);
stroke(0);
lights();
rotateX(rotx);
rotateY(roty);
tox.mesh(mesh, true, 0);
rotx+= 0.00510;
roty+= 0.00620;
mesh.computeFaceNormals();
mesh.computeVertexNormals();

}

void buildMesh() {
mesh=new WETriangleMesh();
toxi.geom.AABB b;
b=new toxi.geom.AABB(80);
b.toMesh(mesh);
}

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Replies(5)

hapticdata

Re: Toxiclibs lighting

2 years ago

Very strange, but I have a solution!

It doesn't appear to be related to performance. Toxiclibs does not really require a big resource-hit that you wouldn't otherwise experience. However Toxi's ToxiclibsSupport class is fairly new, and the bug/unwanted side-effect appears to be in there.

Remove:

tox.mesh(mesh, true, 0);

replace with:

beginShape(TRIANGLES);
for(Iterator i = mesh.faces.iterator();i.hasNext();){
Face f = (Face)i.next();
vertex(f.a.x,f.a.y,f.a.z);
vertex(f.b.x,f.b.y,f.b.z);
vertex(f.c.x,f.c.y,f.c.z);
}
endShape();

and it will work just fine (at least it did for me).

Also, side note. You only change your mesh in your buildMesh() function, so the mesh calls in your draw() are unnecessary. Moving mesh.computeFaceNormals() and mesh.computeVertexNormals() to the end of your buildMesh() function and out of your draw will improve your performance a little.

- Kyle Phillips

ventai

Re: Toxiclibs lighting

2 years ago

Ah lovely, thats sorted it out a treat :) Many thanks. .

tox.mesh(mesh, true, 0); was included in an earlier ray tracing example, but it turns out the modification works too, so great!

The reason I included mesh.computeFaceNormals(); and mesh.computeVertexNormals(); in draw() was because I'm planning to animate vertices and the like while rotating etc. So maybe I would need to leave it in draw(?)

(Really excited about Toxiclibs.js by the way. Excellent stuff :))

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toxmeister

Re: Toxiclibs lighting

2 years ago

Hey guys, you're both jumping the gun here a little too quickly and mislead yourselves!

The slight flickering you're seeing has nothing to do with the library or face or vertex normals, but is simply a result of using the Gouraud shading process on a very low poly mesh and especially one which has only right or obtuse angles between its surface normals (e.g. the corners of a cube). This shading is being used automatically by the P3D & OPENGL renderers when you're using vertex normals, as you did in your original example:

gfx.mesh(myMesh,true); // true = use vertex normals -> gouraud shading

gfx.mesh(myMesh,false); // false = use face normals only -> flat shading

The "correction" Kyle posted above is actually the same result as using "false" with the mesh() function above, only you're asking Processing's PGraphics class to compute the normals for each triangle (which is actually slower, since we already have done this previously and it only needs to be done once for static meshes or after each update of any mesh vertices).

So please, don't jump to wrong conclusions so quickly... Gouraud shading is not always desired, but for example replace the cube with a sphere and you'll see that it much improves the rendering quality compared to flat shading. Another example is the KuryeCloth example bundled with the "verletphysics" module. Also available on OpenProcessing. Press 'g' to toggle between Gouraud and flat shading...

hapticdata

Re: Toxiclibs lighting

2 years ago

I apologize for insinuating the issue was with ToxiclibsSupport. I had never seen the shader act that way previously.Now that I've looked at the mesh method's source it makes sense.

Thanks for the explanation, that is very helpful!

- Kyle Phillips

ventai

Re: Toxiclibs lighting

2 years ago

That's very interesting, thanks for the clarification. .

So it appears I may not need to use:-

mesh.computeFaceNormals();
mesh.computeVertexNormals();

... for low poly count geometry, but will need to with higher count. Is this the case?

Cheers

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