I decided to start playing around with openGL (LWJGL) again after a few years break. This time im actually going to learn how to use VBOs properly, and not use immediate mode like last time. First of all I’d just like to ask for some general advice. Say I have a program with a bunch of objects (or mesh/model whatever you would call it). These objects are kind of static, meaning no animations that would change vertex data. However they may be translated, rotated or scaled. My question is, what is generally the best way to deal with this using VBOs? I can picture two way:
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Setting up the VBO with all the object vertex data and not modifying it further. I would have to loop through every object and send a uniform to the shader depending on its position, rotation, and scale, and then render. This way I don’t have to touch the VBO which is nice, but instead i have to perform a glUniform and a glDrawArrays for every object. This is what I use currently.
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Modify the data in the VBO directly. If I do it this way I don’t have to do any glUniform calls and I could probably just use one glDrawArrays call, but instead I have to modify the data in the VBO, perhaps many times per frame.
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Something else.
I haven’t figured out how to use VBOs properly, so any advice is more than welcome.
Now to the actual problem. Rendering using VBOs causes stuttering. By stuttering I don’t mean lag or fps drop. I can have 5000+ FPS and still stutter. What happens is that occasionally the program freezes for a short time. I’d say around 0.25s on average, but it can vary from maybe 0.1s to 0.5s. These freezes occur maybe once every second or so. It doesn’t seem to matter how many objects I am rendering, the stuttering is still noticeable, even when I’m only rendering 300 vertices. The duration of the freezes seems to increase as I increase the amount of objects I draw, but only a little.
Here’s some code. I removed every thing that is not relevant to this problem.
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import java.nio.FloatBuffer;
import java.util.ArrayList;
import org.lwjgl.BufferUtils;
import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL15;
import org.lwjgl.opengl.GL20;
public class CopyOfMain {
int shaderProgram;
int bufferObject;
PerspectiveCamera camera;
int fps;
float lastFps;
FloatBuffer vertexBuffer;
ArrayList<Cube> cubes = new ArrayList<Cube>();
public void start() {
try {
Display.setDisplayMode(new DisplayMode(800,800));
Display.create();
} catch (LWJGLException e) {
e.printStackTrace();
System.exit(0);
}
GL11.glEnable(GL11.GL_DEPTH_TEST);
GL11.glDepthMask(true);
GL11.glDepthFunc(GL11.GL_LEQUAL);
GL11.glDepthRange(0.0f, 1.0f);
shaderProgram = ShaderLoader.loadShader("res/shader/default.vert", "res/shader/default.frag");
bufferObject = GL15.glGenBuffers();
camera = new PerspectiveCamera(70,Display.getWidth()/(float)Display.getHeight(), 1000, 0.05f);
vertexBuffer = BufferUtils.createFloatBuffer(100 * 6 * 6 * 12 * 4);
for (int i = 0; i<100; i++) {
Cube cube = new Cube();
cube.setScale((float) (Math.random()*2));
cube.setX((float) (Math.random()*40 -20));
cube.setY((float) (Math.random()*40 -20));
cube.setZ((float) (Math.random()*1000 - 998));
cubes.add(cube);
addToVBO(cube);
}
vertexBuffer.flip();
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, bufferObject);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, vertexBuffer, GL15.GL_STATIC_DRAW);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL20.glUseProgram(shaderProgram);
GL20.glUniformMatrix4(GL20.glGetUniformLocation(shaderProgram, "projectionMatrix"), true, (FloatBuffer)BufferUtils.createFloatBuffer(4*16).put(camera.getProjectionMatrix().getData()).flip());
GL20.glUniformMatrix4(GL20.glGetUniformLocation(shaderProgram, "modelMatrix"), true, (FloatBuffer)BufferUtils.createFloatBuffer(4*16).put(new Matrix4x4().toIdentity().getData()).flip());
GL20.glUseProgram(0);
lastFps = (Sys.getTime() * 1000) / Sys.getTimerResolution();
while (!Display.isCloseRequested()) {
if (Keyboard.isKeyDown(Keyboard.KEY_W)) {
camera.setY(camera.getY() + 0.01014f);
}
if (Keyboard.isKeyDown(Keyboard.KEY_S)) {
camera.setY(camera.getY() - 0.01014f);
}
if (Keyboard.isKeyDown(Keyboard.KEY_A)) {
camera.setX(camera.getX() - 0.01014f);
}
if (Keyboard.isKeyDown(Keyboard.KEY_D)) {
camera.setX(camera.getX() + 0.01014f);
}
render();
updateFPS();
Display.update();
//Display.sync(60);
}
Display.destroy();
}
public void addToVBO(Cube cube) {
for (int i = 0; i<cube.getVertices().length; i++) {
vertexBuffer.put(cube.vertices[i].getX());
vertexBuffer.put(cube.vertices[i].getY());
vertexBuffer.put(cube.vertices[i].getZ());
vertexBuffer.put(cube.vertices[i].getU());
vertexBuffer.put(cube.vertices[i].getV());
vertexBuffer.put(cube.vertices[i].getNX());
vertexBuffer.put(cube.vertices[i].getNY());
vertexBuffer.put(cube.vertices[i].getNZ());
vertexBuffer.put(cube.vertices[i].getR());
vertexBuffer.put(cube.vertices[i].getG());
vertexBuffer.put(cube.vertices[i].getB());
vertexBuffer.put(cube.vertices[i].getA());
}
}
public void updateFPS() {
if ((Sys.getTime() * 1000) / Sys.getTimerResolution() - lastFps > 1000) {
Display.setTitle("FPS: " + fps);
fps = 0;
lastFps += 1000;
}
fps++;
}
public void render() {
GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
GL20.glUseProgram(shaderProgram);
GL20.glUniformMatrix4(GL20.glGetUniformLocation(shaderProgram, "viewMatrix"), true, (FloatBuffer)BufferUtils.createFloatBuffer(4*16).put(camera.getViewMatrix().getData()).flip());
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, bufferObject);
GL20.glEnableVertexAttribArray(0);
GL20.glVertexAttribPointer(0, 3, GL11.GL_FLOAT, false, 48, 0);
GL20.glEnableVertexAttribArray(1);
GL20.glVertexAttribPointer(1, 2, GL11.GL_FLOAT, false, 48, 3*4);
GL20.glEnableVertexAttribArray(2);
GL20.glVertexAttribPointer(2, 3, GL11.GL_FLOAT, false, 48, 5*4);
GL20.glEnableVertexAttribArray(3);
GL20.glVertexAttribPointer(3, 4, GL11.GL_FLOAT, false, 48, 8*4);
for (int i = 0; i<cubes.size(); i++) {
Cube m = cubes.get(i);
GL20.glUniformMatrix4(GL20.glGetUniformLocation(shaderProgram, "modelMatrix"), true, (FloatBuffer)BufferUtils.createFloatBuffer(4*16).put(new Matrix4x4().toIdentity().translate(m.x, m.y, m.z).rotateX(m.pitch).rotateY(m.yaw).rotateZ(m.roll).scale(m.scale).getData()).flip());
GL11.glDrawArrays(GL11.GL_TRIANGLES, i*36, 36);
}
GL20.glDisableVertexAttribArray(0);
GL20.glDisableVertexAttribArray(1);
GL20.glDisableVertexAttribArray(2);
GL20.glDisableVertexAttribArray(3);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL20.glUseProgram(0);
}
public static void main(String[] argv) {
CopyOfMain display = new CopyOfMain();
display.start();
}
}
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