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POSwitching between textures in OpenGL ES 2
 

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  1. POSwitching between textures in OpenGL ES 2
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    <p>I'm trying to figure out how to put different textures into different texture units and choose which texture to draw with. I have the following code in my <code>onDrawFrame()</code> method</p> <pre><code> int[] texture = new int[7]; texture[0] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture1); texture[1] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture2); texture[2] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture3); texture[3] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture4); texture[4] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture5); texture[5] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture6); texture[6] =TextureHelper.loadTexture(mActivityContext,R.drawable.texture7); for (int i = 0; i &lt; 7; i ++) { GLES20.glActiveTexture(GLES20.GL_TEXTURE0 + i); GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture[i]); GLES20.glUniform1i(mTextureUniformHandle, i); Matrix.setIdentityM(mModelMatrix, 0); Matrix.translateM(mModelMatrix, 0, -0.60f + 0.2f * i, 0.0f, 0.0f); draw(); } </code></pre> <p>What this is supposed to do is load seven different textures into separate texture units and draw cubes, each cube with a different texture. However, what ends up happening is that all of the cubes end up being drawn with the first texture.</p> <p>It works correctly if I change <code>GLES20.glActiveTexture(GLES20.GL_TEXTURE0 + i)</code> to <code>GLES20.glActiveTexture(GLES20.GL_TEXTURE0)</code> and <code>GLES20.glUniform1i(mTextureUniformHandle, i)</code> to <code>GLES20.glUniform1i(mTextureUniformHandle, 0)</code>, but that just uses a single texture unit and replaces the texture in that unit every time, which is not what I want to do.</p> <p>What am I doing wrong? Thanks in advance.</p> <p>EDIT:</p> <p>Vertex shader:</p> <pre><code> "uniform mat4 u_MVPMatrix;" + // A constant representing the // combined // model/view/projection matrix. "uniform mat4 u_MVMatrix;" + // A constant representing the // combined model/view matrix. "attribute vec4 a_Position;" + // Per-vertex position // information we will pass in. "attribute vec4 a_Color;" + // Per-vertex color information we // will pass in. "attribute vec2 a_TexCoordinate;" + // Per-vertex texture // coordinate information we // will pass in. "varying vec3 v_Position;" + // This will be passed into the // fragment shader. "varying vec4 v_Color;" + // This will be passed into the // fragment shader. "varying vec2 v_TexCoordinate;" + // This will be passed into // the fragment shader. // The entry point for our vertex shader. "void main()" + "{" + // Transform the vertex into eye space. "v_Position = vec3(u_MVMatrix * a_Position);" + // Pass through the color. "v_Color = a_Color;" + // Pass through the texture coordinate. "v_TexCoordinate = a_TexCoordinate;" + // gl_Position is a special variable used to store the final // position. // Multiply the vertex by the matrix to get the final point in // normalized screen coordinates. "gl_Position = u_MVPMatrix * a_Position;" + "} "; </code></pre> <p>Fragment shader:</p> <pre><code> "precision mediump float;" + // Set the default precision to medium. We don't need as high of a // precision in the fragment shader. "uniform sampler2D u_Texture;" + // The input texture. "varying vec3 v_Position;" + // Interpolated position for this fragment. "varying vec4 v_Color;" + // This is the color from the vertex shader interpolated across the // triangle per fragment. "varying vec2 v_TexCoordinate;" + // Interpolated texture coordinate per fragment. // The entry point for our fragment shader. "void main()" + "{" + // Multiply the color by the diffuse illumination level and texture value to get final output color. "gl_FragColor = (v_Color * texture2D(u_Texture, v_TexCoordinate));" + "}"; </code></pre> <p>draw() method:</p> <pre><code>public void draw() { // Pass in the position information mCubePositions.position(0); GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false, 0, mCubePositions); GLES20.glEnableVertexAttribArray(mPositionHandle); // Pass in the color information mCubeColors.position(0); GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false, 0, mCubeColors); GLES20.glEnableVertexAttribArray(mColorHandle); // Pass in the texture coordinate information mCubeTextureCoordinates.position(0); GLES20.glVertexAttribPointer(mTextureCoordinateHandle, mTextureCoordinateDataSize, GLES20.GL_FLOAT, false, 0, mCubeTextureCoordinates); GLES20.glEnableVertexAttribArray(mTextureCoordinateHandle); // This multiplies the view matrix by the model matrix, and stores the // result in the MVP matrix // (which currently contains model * view). Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0); // Pass in the modelview matrix. GLES20.glUniformMatrix4fv(mMVMatrixHandle, 1, false, mMVPMatrix, 0); // This multiplies the modelview matrix by the projection matrix, and // stores the result in the MVP matrix // (which now contains model * view * projection). Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0); // Pass in the combined matrix. GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0); // Draw the cube. GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 6); } </code></pre> <p>Assigning mTextureUniformHandle :</p> <p><code>mTextureUniformHandle = GLES20.glGetUniformLocation(mProgramHandle, "u_Texture");</code></p>
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    1. COThat code looks correct to me. Can you make sure that you don't have any GL errors w/ glGetError? The only thing I can think of is that mTextureUniformHandle is not linked properly. Does it have a valid uniform ID?
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    2. COglGetError(), called right at the end of the for loop, returns 0. How do I check the uniform ID?
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    3. COIf error is zero than I guess your uniform is fine. When I said to check the ID I just meant what is the value of mTextureUniformHandle. Maybe post your shaders just to be sure?
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