GLGraphics GLModel in class

veryphatic

in Contributed Library Questions • 2 years ago

Hi, I'm trying to get my head around creating a particle generator using GLModel.

I have in the main class a call that instantiates the particle controller, then the particle controller updates the vectors.

What I can't figure out is where I need to update the model. As I have one model with max_particles * 4 (I'm using QUADS), my understanding from reading the post about getting started with GLGraphics is that the most efficient way of updating the position is via a FloatBuffer.

I have a Particle class that has an update function, adding the vectors, and an updateVertex function that uses the FloatBuffer to add the positions into the vertices.

What I can't figure out is where do I add the render.model() and updateVertices() functions in my particle controller.

Replies(3)

veryphatic

Re: GLGraphics GLModel in class

2 years ago

Just an update, this is what for the bit where I update the vertices:

for (int i=0; i<MAX_PARTICLES; i++) {
if(particles[i].notDead()) {
// update the particle (velocity)
particles[i].update();
// update the vertex array
blocks.beginUpdateVertices();
// go to the right position in the array
posArray.position(i*8);
// put the float returned from updateVertexArray into the float buffer
posArray.put(particles[i].updateVertexArray(i, posArray));
blocks.endUpdateVertices();
}
}
// render the particles
render.model(blocks);

veryphatic

Re: GLGraphics GLModel in class

2 years ago

Ok, another update, because the last one was really wrong.

So here is the class structure

- Main

+ ParticleController

+ Particle

Within ParticleController I have an updatePosBuffer that passes into the Particle class a copy of itself to update the vertex int buffer, where blocks is the model

for (int i=0; i<numSprites; i++) {
if (particles[i].noDead()) {
// update the position of the particles
blocks.beginUpdateVertices();
// update the position buffer
particles[i].updatePosBuffer(i, this);
blocks.endUpdateVertices();
// render the particle
render.model(blocks, i, i*8);
}
}

Then in the Particle class's updatePosBuffer function, where pc is a reference to the Particle Controller:

// get access to the buffer stored in the particle controller
pc.blocks.vertices.position(i*8);
// x1, y1
pc.blocks.vertices.put(loc.x);
pc.blocks.vertices.put(loc.y);
// x2, y1
pc.blocks.vertices.put(loc.x + particleWidth);
pc.blocks.vertices.put(loc.y);
// x2, y2
pc.blocks.vertices.put(loc.x + particleWidth);
pc.blocks.vertices.put(loc.y + particleHeight);
// x1, y2
pc.blocks.vertices.put(loc.x);
pc.blocks.vertices.put(loc.y + particleHeight);

Its not working, I'm thinking that is has something to do with the way the model was setup..?

andres

Re: GLGraphics GLModel in class

2 years ago

One problem is the indexing that you seem to be using in your code: pc.blocks.vertices.position(i*8)

Since you are defining each particle as a quad formed by 4 vertices, and each vertex takes 4 components (xyzw, although w is not used), you should do pc.blocks.vertices.position(i* 4 * 4).

The other comment I have is that you shouldn't call render.model(blocks, i, i*16) for each particle, this can result in a much lower performance. It is better to update all the vertices first, and then render the entire model in a single render call at the end.

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