Thread: Making sprites opengl

Hello C programming board

This question might be a little silly but I don't know the answer so I'm asking for help.

I have made it to the point where I can load textures *even atlas textures* and pull out a sub region, and also draw that region on call. I'll show code below.

My question how is how do I create a sprite class. I want it to eventually be able to support sprite batching but I am coming up a little empty right now. Here is my sprite class.

Code:

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;


import android.opengl.GLES20;


public class Sprite {
    final public float[] vertices = new float[20];
    final public short[] indices = new short[6];
    public FloatBuffer vertBuffer;
    public FloatBuffer texBuffer;
    public ShortBuffer indxBuffer;
    Texture texture;    
    public float width;
    public float height;
    public float sMin, sMax, tMin, tMax;
    
    public Sprite(SpriteSheetRegion region){    
        this.texture = region.texture;
        this.width =  region.width;
        this.height = region.height;
        this.sMax = region.sMax;
        this.sMin = region.sMin;
        this.tMax = region.tMax;
        this.tMin = region.tMin;
    
        vertices[0] = -width*0.5f;
        vertices[1] = -height*0.5f;
        vertices[2] = 0.0f;
        vertices[3] = sMin;
        vertices[4] = tMax;
        vertices[5] = width*0.5f;
        vertices[6] = -height*0.5f;
        vertices[7] = 0.0f;
        vertices[8] = sMax;
        vertices[9] = tMax;
        vertices[10] = -width*0.5f;
        vertices[11] = height*0.5f;
        vertices[12] = 0.0f;
        vertices[13] = sMin;
        vertices[14] = tMin;
        vertices[15] = width*0.5f;
        vertices[16] = height*0.5f;
        vertices[17] = 0.0f;
        vertices[18] = sMax;
        vertices[19] = tMin;
        
        System.out.println((width*0.5f)+" "+(height*0.5f));
        
        indices[0] = 0;
        indices[1] = 1;
        indices[2] = 2;
        indices[3] = 2;
        indices[4] = 1;
        indices[5] = 3;
        
        vertBuffer = ByteBuffer.allocateDirect(vertices.length*4).order(ByteOrder.nativeOrder()).asFloatBuffer();
        vertBuffer.put(vertices).position(0);
        indxBuffer = ByteBuffer.allocateDirect(indices.length*2).order(ByteOrder.nativeOrder()).asShortBuffer();
        indxBuffer.put(indices).position(0);
    }
    
    public Sprite(SpriteSheetRegion region, float width, float height){    
        this.texture = region.texture;
        this.width =  width;
        this.height = height;
        this.sMax = region.sMax;
        this.sMin = region.sMin;
        this.tMax = region.tMax;
        this.tMin = region.tMin;
    
        vertices[0] = -width*0.5f;
        vertices[1] = -height*0.5f;
        vertices[2] = 0.0f;
        vertices[3] = sMin;
        vertices[4] = tMax;
        vertices[5] = width*0.5f;
        vertices[6] = -height*0.5f;
        vertices[7] = 0.0f;
        vertices[8] = sMax;
        vertices[9] = tMax;
        vertices[10] = -width*0.5f;
        vertices[11] = height*0.5f;
        vertices[12] = 0.0f;
        vertices[13] = sMin;
        vertices[14] = tMin;
        vertices[15] = width*0.5f;
        vertices[16] = height*0.5f;
        vertices[17] = 0.0f;
        vertices[18] = sMax;
        vertices[19] = tMin;
        
        indices[0] = 0;
        indices[1] = 1;
        indices[2] = 2;
        indices[3] = 2;
        indices[4] = 1;
        indices[5] = 3;
        
        vertBuffer = ByteBuffer.allocateDirect(vertices.length*4).order(ByteOrder.nativeOrder()).asFloatBuffer();
        vertBuffer.put(vertices).position(0);
        indxBuffer = ByteBuffer.allocateDirect(indices.length*2).order(ByteOrder.nativeOrder()).asShortBuffer();
        indxBuffer.put(indices).position(0);
    }
    
    
    public void draw(int program){
        GLES20.glUseProgram(program);
        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture.id);
        
        vertBuffer.position(0);
        GLES20.glVertexAttribPointer(GLES20.glGetAttribLocation(program, "aPos"), 3, GLES20.GL_FLOAT, false, 20, vertBuffer);
        GLES20.glEnableVertexAttribArray(GLES20.glGetAttribLocation(program, "aPos"));


        vertBuffer.position(3);
        GLES20.glVertexAttribPointer(GLES20.glGetAttribLocation(program, "aTexPos"), 2, GLES20.GL_FLOAT, false, 20, vertBuffer);
        GLES20.glEnableVertexAttribArray(GLES20.glGetAttribLocation(program, "aTexPos"));
        
        GLES20.glUniform1i(GLES20.glGetUniformLocation(program, "texture"), 0);
        GLES20.glDrawElements(GLES20.GL_TRIANGLES, 6, GLES20.GL_UNSIGNED_SHORT, indxBuffer);
    }
    
    @Override
    public String toString(){
        return texture.toString();
    }
}

I basically took all the code I had in my rendering function and put it in the sprite class, from binding the textures and all. For instance, I have no idea how to rotate this sprite. Well Actually I could put a model matrix inside the sprite class but I get the feeling that's going down the wrong road. I can move the sprite horizontally by adding some uniform value to the x vertices or horizontally by adding some uniform value to the y vertices but again I feel that's going down the wrong path but honestly I don't know. Here is my rendering code now.

Code:

public void onDrawFrame(GL10 gl) {
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
        GLES20.glUseProgram(sProgram);
    
    
        Matrix.setIdentityM(modelMatrix, 0);
        Matrix.translateM(modelMatrix, 0, 0.0f, 0.0f, -1.0f);


        Matrix.multiplyMM(cam.combMatrix, 0, cam.viewMatrix, 0, modelMatrix, 0);
        Matrix.multiplyMM(cam.combMatrix, 0, cam.projMatrix, 0, cam.combMatrix, 0);
        GLES20.glUniformMatrix4fv(GLES20.glGetUniformLocation(sProgram, "MVPMat"), 1, false, cam.combMatrix, 0);
        
        sp.draw(sProgram);
    }

I really hope someone with a little more experience can help me out with this.
quick edit!
added videos:
1. http://www.youtube.com/watch?v=TECYZN2udSA&feature=plcp
translated, rotated, and scaled based on the camera view matrix

2.http://www.youtube.com/watch?v=0aYOIWyDiCk&feature=plcp
similar but larger image loaded.

the difference in videos show that i can get texture atlas sub regions w/o changing my code, just pass in the name of the texture sub region and do sprite.draw(glprogram);