GLGraphics and objLoader

Florian S..

in Contributed Library Questions • 2 years ago

I try to load a model with saito .objLoader and want to push it into a GLModel for performance reasons. Sadly I don’t get the vertices connected in the right way. Any ideas what I can do? The model is exported from Photoshop. The screenshots show objloader on the left and glmodel on the right.

import processing.opengl.*;
import codeanticode.glgraphics.*;
import saito.objloader.*;
OBJModel model;
GLModel glmodel;
void setup() {
size(300, 200, GLConstants.GLGRAPHICS);
model = new OBJModel(this, "Model.obj", "relative", POLYGON);
model.enableDebug();
glmodel = new GLModel(this, model.getVertexCount(), POLYGON, GLModel.STATIC);
glmodel.beginUpdateVertices();
for(int i = 0; i < model.getVertexCount(); i++){
PVector v = model.getVertex(i);
glmodel.updateVertex(i, v.x, v.y, v.z);
}
glmodel.endUpdateVertices();
glmodel.initColors();
glmodel.setColors(255, 100);
noStroke();
}
void draw() {
background(0);
ambient(250, 250, 250);
pointLight(255, 255, 255, 500, height/2, 400);
// draw objloader model
model.draw();
translate(50, 0, 0);
// draw glmodel
rotateX((float) mouseX / 100);
translate(30, 0, 0);
GLGraphics renderer = (GLGraphics)g;
renderer.beginGL();
renderer.model(glmodel);
renderer.endGL();
}

Replies(6)

andres

Re: GLGraphics and objLoader

2 years ago

The problem is that using POLYGON mode in GLModel results in all the vertices being connected into a single polygonal shape. But this is incorrect, since the geometry in a .obj file is divided in faces, each of which is a separate polygon.

However, I think that most of the time the polygonal faces in the .obj files are just triangles. The vertices are not listed sequentially, but you can get this information from the OBJModel class. So in the case that the faces are triangles, you could do something like this:

model = new OBJModel(this, "Model.obj", "relative", TRIANGLES);
glmodel = new GLModel(this, model.getVertexCount(), TRIANGLES, GLModel.STATIC);
glmodel.beginUpdateVertices();
int i = 0;
for (int f = 0; f < model.getFaceCount(); f++) {
PVector[] fverts = model.getFaceVertices(f);
for (int v = 0; v < fverts.length; v++) {
glmodel.updateVertex(i++, fverts[v].x, fverts[v].y, fverts[v].z);
}
}
glmodel.endUpdateVertices();

This simple code would discard any additional information read by the objloader (normals, colors, etc), take a look at the documentation of the OBJModel class to see what other methods you can use to retrieve more data from the model.

Florian S..

Re: GLGraphics and objLoader

2 years ago

Oh yes this works! I just had to change one argument in the GLModel constructor from model.getVertexCount() to model.getFaceCount() * 3

Yes, yes :) Thank you!

mr.t

Re: GLGraphics and objLoader

2 years ago

to even dive deeper into this, i tried passing the normals for lights.

but things get really messy. I assume the faces and normals are not in sync.

What's the right way to do it!?

my approach:

for (int k = 0; k < modelOBJ.getFaceCount(); k++) {
PVector[] faceVertices = modelOBJ.getFaceVertices(k);
for (int i = 0; i < faceVertices.length; i++) {
            theModel.updateVertex(id, faceVertices[i].x, faceVertices[i].y, faceVertices[i].z);
                id++;
            }
        }
theModel.endUpdateVertices();
theModel.initNormals();
theModel.beginUpdateNormals();
for (int i = 0; i < modelOBJ.getNormalCount(); i++) {
PVector normals = modelOBJ.getNormal(i);
theModel.updateNormal(i,normals.x,normals.y,normals.z);
}
theModel.endUpdateNormals();

Florian S..

Re: GLGraphics and objLoader

2 years ago

Some weeks ago I used this but I’m not sure if it is correct. At least for my purpose it looked right: https://gist.github.com/1173825

mr.t

Re: GLGraphics and objLoader

2 years ago

uhh.. great thanx!

i tried it by just calculating it myself with:

   theModel.beginUpdateVertices();
        int i = 0;
          for (int f = 0; f < modelOBJ.getFaceCount(); f++) {
            PVector[] fverts = modelOBJ.getFaceVertices(f);
            for (int v = 0; v < fverts.length; v++) {
              theModel.updateVertex(i++, fverts[v].x, fverts[v].y, fverts[v].z);
              PVector vertNorm = PVector.div(fverts[v], fverts[v].mag());
              normals.add(vertNorm);
            }
          }
        theModel.endUpdateVertices();
theModel.initNormals();
theModel.updateNormals(normals);

but the result was very dull!

your's looks much more crisp and there is some reflection now, exactly what i was trying to get!

Florian S..

Re: Re: GLGraphics and objLoader

2 years ago

Yes I had some headaches with this and deep dives into the code of OBJLoader. In the end I also had reflection using a cubemap. Nice to hear that it seems to work for you as well, Marc :)

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