CODEWITHSUNDEEP
androidopengl-es
Savail
Savail

Reputation: 867

Opengl Es 2.0 - Displaying multiple textures

So I'm able to display 1 texture at a time but I have a problem with displaying more textures. The render function is called for every texture separately (tex_nr), not sure if that's a good approach. Here's the rendering code:

private void Render(float[] m, int tex_nr) {

        // Set our shaderprogram to image shader
        GLES20.glUseProgram(riGraphicTools.sp_Image);

        // clear Screen and Depth Buffer, we have set the clear color as black.
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

        // get handle to vertex shader's vPosition member
        int mPositionHandle = GLES20.glGetAttribLocation(riGraphicTools.sp_SolidColor, "vPosition");

        // Enable generic vertex attribute array
        GLES20.glEnableVertexAttribArray(mPositionHandle);

        // Prepare the triangle coordinate data
        GLES20.glVertexAttribPointer(mPositionHandle, 3,
                                     GLES20.GL_FLOAT, false,
                                     0, vertexBuffer);

     // Get handle to texture coordinates location
        int mTexCoordLoc = GLES20.glGetAttribLocation(riGraphicTools.sp_Image,
                             "a_texCoord" );

        // Enable generic vertex attribute array
        GLES20.glEnableVertexAttribArray ( mTexCoordLoc );

        // Prepare the texturecoordinates
        GLES20.glVertexAttribPointer ( mTexCoordLoc, 2, GLES20.GL_FLOAT,
                      false,
                      0, uvBuffer);

        // Get handle to shape's transformation matrix
        int mtrxhandle = GLES20.glGetUniformLocation(riGraphicTools.sp_Image,
                           "uMVPMatrix");

        // Apply the projection and view transformation
        GLES20.glUniformMatrix4fv(mtrxhandle, 1, false, m, 0);

        // Get handle to textures locations
        int mSamplerLoc = GLES20.glGetUniformLocation (riGraphicTools.sp_Image,
                            "s_texture" );

        // Set the sampler texture unit to where we have saved the texture.
        GLES20.glUniform1i ( mSamplerLoc, tex_nr);

        // Draw the triangle
        GLES20.glDrawElements(GLES20.GL_TRIANGLES, indices.length,
                 GLES20.GL_UNSIGNED_SHORT, drawListBuffer);

        // Disable vertex array
        GLES20.glDisableVertexAttribArray(mPositionHandle);
        GLES20.glDisableVertexAttribArray(mTexCoordLoc);

    }

And here the loading textures code:

texturenames = new int[GameObject.spritePaths.size()];
        GLES20.glGenTextures(GameObject.spritePaths.size(), texturenames, 0);
        for(int i = 0; i < GameObject.spritePaths.size(); i++)
        {
            // Retrieve our image from resources.
            int id = mContext.getResources().getIdentifier(GameObject.spritePaths.get(i), null, mContext.getPackageName());

            // Temporary create a bitmap
            Bitmap bmp = BitmapFactory.decodeResource(mContext.getResources(), id);

            // Bind texture to texturename
            GLES20.glActiveTexture(GLES20.GL_TEXTURE0+i);
            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texturenames[i]);

            // Set filtering
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);

            // Load the bitmap into the bound texture.
            GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bmp, 0);

            // We are done using the bitmap so we should recycle it.
            bmp.recycle();
        }

As a result of this code, only the last loaded texture is displayed and I have no idea why the former ones do not show up. I would be very grateful for any clues! edit: Actually, I have just found out that I can display all of the textures that I loaded but only 1 at a time. So I guess that the problem isn't connected with loading? It looks as if each consecutive Render call(my function) prevented the drawing in the previous call...

Upvotes: 1

Views: 2586

Answers (1)

Reto Koradi
Reto Koradi

Reputation: 54572

You have a call to glClear() in your Render() method:

// clear Screen and Depth Buffer, we have set the clear color as black.
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

This does pretty much what the name suggests, and what's also captured in your comment: It clears all rendering that has been done so far. So if you call the Render() method multiple times, only the rendering from the last call will be visible.

If you want to invoke Render() multiple times for the same frame, you will need to take it out of Render(), and call it only once at the start of rendering the frame.

There's another thing in your code that looks slightly suspicious:

int mPositionHandle = GLES20.glGetAttribLocation(riGraphicTools.sp_SolidColor, "vPosition");
....
int mTexCoordLoc = GLES20.glGetAttribLocation(riGraphicTools.sp_Image, "a_texCoord");

Unless sp_SolidColor and sp_Image have the same value, you're querying attribute locations from two different shader programs. Since sp_Image is the program you are using, you should pass it in as the first parameter for both these calls.

Upvotes: 1

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