snuvi-engine/src/me/hammerle/snuviengine/api/ColorRenderer.java

package me.hammerle.snuviengine.api;

import java.nio.ByteBuffer;
import org.lwjgl.BufferUtils;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL15.*;
import static org.lwjgl.opengl.GL20.*;
import static org.lwjgl.opengl.GL30.*;

public class ColorRenderer
{
    private int vao;
    private int vbo;
    
    private ByteBuffer buffer = BufferUtils.createByteBuffer(48);
    
    private final static int BUFFER_BYTE_LENGTH = 1024 * 1024;
    private final static int OBJECT_LENGTH = 64;
    
    private int offset = BUFFER_BYTE_LENGTH - OBJECT_LENGTH;
    
    private float depth = 0.0f;
    
    protected ColorRenderer()
    {
        Shader.addTask(() -> 
        {
            vao = glGenVertexArrays();
            vbo = glGenBuffers();
            
            GLHelper.glBindVertexArray(vao);
            GLHelper.glBindBuffer(vbo);
            
            glEnableVertexAttribArray(0);
            glEnableVertexAttribArray(2);
            
            glVertexAttribPointer(0, 3, GL_FLOAT, false, 16, 0);
            glVertexAttribPointer(2, 4, GL_UNSIGNED_BYTE, true, 16, 12);
        });
    }
    
    public void setDepth(float depth)
    {
        this.depth = depth;
    }

    public void drawRectangle(float minX, float minY, float maxX, float maxY, int color)
    {
        GLHelper.glBindBuffer(vbo);
        
        offset += OBJECT_LENGTH;
        if(offset + OBJECT_LENGTH >= BUFFER_BYTE_LENGTH)
        {
            offset = 0;
            glBufferData(GL_ARRAY_BUFFER, BUFFER_BYTE_LENGTH, GL_STREAM_DRAW);
        }
        buffer = glMapBufferRange(GL_ARRAY_BUFFER, offset, OBJECT_LENGTH, GL_MAP_WRITE_BIT | GL_MAP_UNSYNCHRONIZED_BIT, buffer);
        if(buffer == null)
        {
            return;
        }
        
        float fcolor = Float.intBitsToFloat(color);
        
        buffer.putFloat(minX);
        buffer.putFloat(maxY);   
        buffer.putFloat(depth);  
        buffer.putFloat(fcolor);
        
        buffer.putFloat(minX);
        buffer.putFloat(minY);   
        buffer.putFloat(depth);  
        buffer.putFloat(fcolor);
        
        buffer.putFloat(maxX);
        buffer.putFloat(maxY);  
        buffer.putFloat(depth);  
        buffer.putFloat(fcolor);
        
        buffer.putFloat(maxX);
        buffer.putFloat(minY);  
        buffer.putFloat(depth);  
        buffer.putFloat(fcolor);
        
        buffer.flip();

        glUnmapBuffer(GL_ARRAY_BUFFER);
        
        GLHelper.glBindVertexArray(vao);
        glDrawArrays(GL_TRIANGLE_STRIP, offset / 16, 4);
    }
}