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

package me.hammerle.snuviengine.api;

public final class MatrixStack {
    private final int capacity;
    private final float[][] stack;
    private int index = 0;

    protected MatrixStack(int capacity) {
        this.capacity = capacity;
        stack = new float[capacity][16];
        stack[index][0] = 1.0f;
        stack[index][5] = 1.0f;
        stack[index][10] = 1.0f;
        stack[index][15] = 1.0f;
    }

    protected float[] getData() {
        return stack[index];
    }

    protected boolean push() {
        if(index + 1 >= capacity) {
            return false;
        }
        index++;
        System.arraycopy(stack[index - 1], 0, stack[index], 0, 16);
        return true;
    }

    protected boolean pop() {
        if(index - 1 < 0) {
            return false;
        }
        index--;
        return true;
    }

    protected void scale(float sx, float sy) {
        stack[index][0] *= sx;
        stack[index][1] *= sx;
        stack[index][4] *= sy;
        stack[index][5] *= sy;
    }

    protected void translate(float tx, float ty) {
        stack[index][12] += stack[index][0] * tx + stack[index][4] * ty;
        stack[index][13] += stack[index][1] * tx + stack[index][5] * ty;
    }

    protected void translateTo(float tx, float ty) {
        stack[index][0] = 1.0f;
        stack[index][1] = 0.0f;
        stack[index][4] = 0.0f;
        stack[index][5] = 1.0f;
        stack[index][12] = tx;
        stack[index][13] = ty;
    }

    protected void rotate(float angle) {
        angle = (float) Math.toRadians(angle);
        float cos = (float) Math.cos(angle);
        float sin = (float) Math.sin(angle);

        float a1 = stack[index][0];
        float a2 = stack[index][4];
        stack[index][0] = a1 * cos - a2 * sin;
        stack[index][4] = a1 * sin + a2 * cos;

        a1 = stack[index][1];
        a2 = stack[index][5];
        stack[index][1] = a1 * cos - a2 * sin;
        stack[index][5] = a1 * sin + a2 * cos;
    }
}