P3D - colors don't look right at surface edges

Core Library Questions

dangries

P3D - colors don't look right at surface edges

in Core Library Questions • 2 months ago

I'm working on creating some custom surfaces, using PShape objects, and I'm noticing some unpleasant edge coloring effects. To test this, I also rendered a standard sphere, with the standard lights(); function call, and this is the result:

Note the white edges along the left and lower-left edge of the surface. Has anyone seen this before? Are there known issues related to this? Is this a hardware issue? I'm getting this on two different Windows machines. Are there any magic ways to avoid this?

Any insight would be appreciated!

Replies(5)

amnon.owed

Re: P3D - colors don't look right at surface edges

2 months ago

The cause may be normals. Incorrect or non-supplied normals can cause these type of lighting issues.

Try creating a sphere manually and setting the per-vertex normals correctly. Then compare.

dangries

Re: P3D - colors don't look right at surface edges

2 months ago

I created some of my own surfaces, and computed normals manually, and saw the same behavior. I'll check the normals but I have a feeling this is a rendering issue, or perhaps a z-sorting issue (maybe those white edges are polygons that should actually be obscured by other polygons).

dangries

Re: Re: P3D - colors don't look right at surface edges

2 months ago

Actually, I don't think it's related to z-sorting.

Here's some example code. The spere resolution is set to something low to make the issue more apparent. Anyone want to give it a try and tell me if you see the same thing?

float cameraAngle;
float cameraAngleInc;
PShape sphere;
void setup() {
size(400,400,P3D);
smooth(8);
noStroke();
sphereDetail(10,10);
sphere = createShape(SPHERE, 150);
cameraAngle = 0;
cameraAngleInc = TWO_PI/600;
}
void draw() {
cameraAngle += cameraAngleInc;
camera(500*cos(cameraAngle),300,500*sin(cameraAngle),0,0,0,0,-1,0);
directionalLight(204,204,204,0,-1,0);
ambientLight(24,24,24);
background(0);
shape(sphere);
}
void keyPressed() {
saveFrame("frame_####.png");
}

asimes

Re: P3D - colors don't look right at surface edges

2 months ago

Yes, I also see it

dangries

Re: P3D - colors don't look right at surface edges

2 months ago

Yeah, I think maybe this is a bug. It's probably not something easy to fix...I have no clue. I think obscured polygons are affecting the shading of visible vertices that are attached to them. I posted an issue here:

https://github.com/processing/processing/issues/2018

Wish I were clever enough to investigate the Processing source code on my own, but I'm afraid I'm not!

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