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

package me.hammerle.snuviengine.api;

import java.nio.FloatBuffer;
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 TextureRenderer
{
    private int vao;
    private int vbo;
    
    private int triangles = 0;
    private FloatBuffer buffer;
    
    private boolean built = false;
    
    public TextureRenderer(int triangles)
    {
        buffer = BufferUtils.createFloatBuffer(triangles * 12);
        Shader.addTask(() -> 
        {
            vao = glGenVertexArrays();
            vbo = glGenBuffers();

            GLHelper.glBindVertexArray(vao);
            GLHelper.glBindBuffer(vbo);

            glEnableVertexAttribArray(0);
            glVertexAttribPointer(0, 2, GL_FLOAT, false, 16, 0);

            glEnableVertexAttribArray(1);  
            glVertexAttribPointer(1, 2, GL_FLOAT, false, 16, 8);
        });
    }
    
    public void addTriangle(float x1, float y1, float x2, float y2, float x3, float y3, float tx1, float ty1, float tx2, float ty2, float tx3, float ty3)
    {
        if(buffer.position() + 12 > buffer.capacity())
        {
            FloatBuffer newBuffer = BufferUtils.createFloatBuffer(buffer.capacity() * 2);
            buffer.flip();
            newBuffer.put(buffer);
            buffer = newBuffer;
        }
        
        buffer.put(x1);
        buffer.put(y1);        
        buffer.put(tx1);
        buffer.put(ty1);
        
        buffer.put(x2);
        buffer.put(y2);        
        buffer.put(tx2);
        buffer.put(ty2);
        
        buffer.put(x3);
        buffer.put(y3);        
        buffer.put(tx3);
        buffer.put(ty3);
        
        triangles++;
    }
    
    public void addRectangle(float minX, float minY, float maxX, float maxY, float tMinX, float tMinY, float tMaxX, float tMaxY)
    {
        addTriangle(minX, maxY, minX, minY, maxX, maxY, tMinX, tMaxY, tMinX, tMinY, tMaxX, tMaxY);
        addTriangle(maxX, maxY, minX, minY, maxX, minY, tMaxX, tMaxY, tMinX, tMinY, tMaxX, tMinY);
    }
    
    public boolean isBuilt()
    {
        return built;
    }
    
    public void build()
    {
        if(!Shader.initDone)
        {
            throw new ShaderException("build called too early");
        }
        if(triangles == 0 || built)
        {
            return;
        }
        buffer.flip();
        GLHelper.glBindVertexArray(vao);
        GLHelper.glBindBuffer(vbo);
        glBufferData(GL_ARRAY_BUFFER, buffer, GL_STATIC_DRAW);
        
        buffer.limit(buffer.capacity());
        built = true;
    }
    
    public void clear()
    {
        triangles = 0;
        built = false;
    }
    
    public void draw()
    {
        if(triangles == 0)
        {
            return;
        }
        if(!built)
        {
            throw new ShaderException("build must be called before drawing");
        }
        GLHelper.glBindVertexArray(vao);
        GLHelper.glBindBuffer(vbo);
        glDrawArrays(GL_TRIANGLES, 0, buffer.limit() / 4);
    }
    
    public void delete()
    {
        buffer = null;
        glDeleteVertexArrays(vao);
        glDeleteBuffers(vbo);
        vao = -1;
        vbo = -1;
        built = false;
    }
}