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 final int vertexArray;
    private final int vertexBuffer;
    private int triangles = 0;
    private FloatBuffer buffer;
    private boolean built = false;

    public TextureRenderer(int triangles) {
        buffer = BufferUtils.createFloatBuffer(triangles * 12);
        vertexArray = glGenVertexArrays();
        vertexBuffer = glGenBuffers();
        GLHelper.glBindVertexArray(vertexArray);
        GLHelper.glBindBuffer(vertexBuffer);
        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;
        }
        addToBuffer(x1, y1, tx1, ty1);
        addToBuffer(x2, y2, tx2, ty2);
        addToBuffer(x3, y3, tx3, ty3);
        triangles++;
    }

    private void addToBuffer(float x, float y, float tx, float ty) {
        buffer.put(x);
        buffer.put(y);
        buffer.put(tx);
        buffer.put(ty);
    }

    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(triangles == 0 || built) {
            return;
        }
        buffer.flip();
        GLHelper.glBindVertexArray(vertexArray);
        GLHelper.glBindBuffer(vertexBuffer);
        glBufferData(GL_ARRAY_BUFFER, buffer, GL_STATIC_DRAW);
        buffer.limit(buffer.capacity());
        built = true;
    }

    public void clear() {
        triangles = 0;
        buffer.clear();
        built = false;
    }

    public void draw() {
        if(triangles == 0 || !built) {
            return;
        }
        GLHelper.glBindVertexArray(vertexArray);
        GLHelper.glBindBuffer(vertexBuffer);
        glDrawArrays(GL_TRIANGLES, 0, triangles * 3);
    }

    public void delete() {
        buffer = null;
        glDeleteVertexArrays(vertexArray);
        glDeleteBuffers(vertexBuffer);
        built = false;
    }
}