Question

I’m trying to modernize my OpenGL code a little bit by bringing it to OpenGL 2.0 time, but all I get is a black screen… perhaps someone spots a mistake in my code (not that much of code).

Here is a snip of the relevant bits of my old, fully working code.

// Send color data into GPU memory
glEnableClientState(GL_COLOR_ARRAY);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, colorsHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, colors, GL15.GL_DYNAMIC_DRAW);
glColorPointer(4, GL_FLOAT, 0, 0);

// Send vertex data into GPU memory
glEnableClientState(GL_VERTEX_ARRAY);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, verticesHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, GL15.GL_DYNAMIC_DRAW);
glVertexPointer(3, GL_FLOAT, 0, 0);

// Send texcoords data into GPU memory
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, texcoordsHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, GL15.GL_DYNAMIC_DRAW);
glTexCoordPointer(2, GL_FLOAT, 0, 0);

for (Batch batch : batches) batch.render();

glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);

… batch calls glDrawArrays (amongst doing some opengl state changes) …

glDrawArrays(GL_QUADS, spriteOffset * 4, spriteCount * 4);

And here is the new code:

// Send color data into GPU memory
GL20.glEnableVertexAttribArray(0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, colorsHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, colors, GL15.GL_DYNAMIC_DRAW);
GL20.glVertexAttribPointer(0, 4, GL_FLOAT, false, 0, 0);

// Send vertex data into GPU memory
GL20.glEnableVertexAttribArray(1);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, verticesHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, vertices, GL15.GL_DYNAMIC_DRAW);
GL20.glVertexAttribPointer(1, 3, GL_FLOAT, false, 0, 0);

// Send texcoords data into GPU memory
GL20.glEnableVertexAttribArray(2);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, texcoordsHandle);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, texcoords,GL15.GL_DYNAMIC_DRAW);
GL20.glVertexAttribPointer(2, 2, GL_FLOAT, false, 0, 0);

for (Batch batch : batches) batch.render();

GL20.glDisableVertexAttribArray(0);
GL20.glDisableVertexAttribArray(1);
GL20.glDisableVertexAttribArray(2);

Like I said the first bit of code works perfectly, but the second does not draw anything at all. Those are the only lines of code I changed in my renderer, and they look correct to me. But obviously there is a problem somewhere… What could possibly cause the absence of rendering?

Answer 1

If those are really the only lines you’ve changed, then I guess you haven’t implemented any shaders?

In OpenGLES 2.0 there is no fixed function pipeline, so you need to write vertex/fragment shaders, compile them, link program objects, etc.

I’m sure you can find many tutorials for this if you search.