Shape.getVertexY returning always same data ?

Programming Questions

Emmanuel ..

Shape.getVertexY returning always same data ?

in Programming Questions • 17 days ago

Hello,

I'm making some test with a cube I created, I'm trying to detect the side facing bottom or top or ...

But when I use the getVertex or getVerterX/Y/Z I always get the same value from the vertices even if my cube is moving and rotating.

My cube :

void createCube() {
s = createShape();
s.beginShape(QUAD);
s.fill(col, alpha);
//bottom
s.vertex(-size/2, -size/2, size/2);
s.vertex(size/2, -size/2, size/2);
s.vertex(size/2, -size/2, -size/2);
s.vertex(-size/2, -size/2, -size/2);
//left
s.vertex(-size/2, -size/2, -size/2);
s.vertex(-size/2, -size/2, size/2);
s.vertex(-size/2, size/2, size/2);
s.vertex(-size/2, size/2, -size/2);
//top
s.vertex(-size/2, size/2, -size/2);
s.vertex(size/2, size/2, -size/2);
s.vertex(size/2, size/2, size/2);
s.vertex(-size/2, size/2, size/2);
//front
s.vertex(-size/2, size/2, size/2);
s.vertex(-size/2, -size/2, size/2);
s.vertex(size/2, -size/2, size/2);
s.vertex(size/2, size/2, size/2);
//right
s.vertex(size/2, size/2, size/2);
s.vertex(size/2, -size/2, size/2);
s.vertex(size/2, -size/2, -size/2);
s.vertex(size/2, size/2, -size/2);
//back
s.vertex(size/2, size/2, -size/2);
s.vertex(size/2, -size/2, -size/2);
s.vertex(-size/2, -size/2, -size/2);
s.vertex(-size/2, size/2, -size/2);
s.endShape();
}
void update()
{
translate.add(speed);
position.add(translate);
}
void display() {
pushMatrix();
s.translate(translate.x/frameRate,translate.y/frameRate,translate.z/frameRate);
translate.set(0,0,0);
s.rotateX(rot.x/frameRate);s.rotateY(rot.y/frameRate);s.rotateZ(rot.z/frameRate);
rot.set(0,0,0);
shape(s);
popMatrix();
}

When I try a s.getVertexY/... I get always the same thing...

What am I doing wrong ?

Best regards,

E.D

Replies(3)

andres

Re: Shape.getVertexY returning always same data ?

16 days ago

This is correct, the reason is that the xyz coordinates of the shape are not modified, because the geometry transformations are stored in a matrix that is applied to the vertices only when the shape is rendered.

Emmanuel ..

Re: Shape.getVertexY returning always same data ?

16 days ago

Oh I see now how the data are stored !

If I want to always know where the vertices are what is the best way ?

Should I stock them in Array of PVector and update them everytime ?`Or is it a simpler way to do it ?

andres

Re: Shape.getVertexY returning always same data ?

16 days ago

Unfortunately, there is no easy way to get the transformed coordinates out of a PShape. You could store the original values in PVector array as you say, and keep track of the transformations manually with your own PMatrix, so you can apply it to your array every time you need the transformed coords.

PShape has a getTessellation() method that returns the tessellated geometry (this is, after it had all the transformations applied and converted into triangles). This will actually give you the transformed coordinates, but will also be slow specially for large geometries, because getTessellation() creates a new PShape every time you call it.

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