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Thread: Shader error and Identity Matrix

  1. #1
    Junior Member Newbie
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    Apr 2013
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    Shader error and Identity Matrix

    Hi. I have a simple shader line gl_Position = u_MVPMatrix *(u_InverseBindMatrix) *(a_Position); I have u_inversebindmatrix set to Identity matrix using Matrix.setidentityM(); If I render without the line *u_InverseBindMatrix, then my cube shows up. If I leave it in, however, nothing shows up. I thought the identity matrix left equations unchanged. Any ideas?

  2. #2
    Senior Member OpenGL Guru
    Join Date
    May 2009
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    4,948
    You might want to consider that you're not setting the matrix properly. Of course, we can't actually know that since you didn't show us your code...

  3. #3
    Junior Member Newbie
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    Apr 2013
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    This is the shader and the draw code.
    Code :
    	protected String getVertexShader()
    	{
    		// TODO: Explain why we normalize the vectors, explain some of the vector math behind it all. Explain what is eye space.
    		final String vertexShader =
    			"uniform mat4 u_MVPMatrix;      \n"		// A constant representing the combined model/view/projection matrix.
    		  + "uniform mat4 u_MVMatrix;       \n"		// A constant representing the combined model/view matrix.	
    		  + "uniform vec3 u_LightPos;       \n"	    // The position of the light in eye space.
    		  +" uniform mat4 u_BindShapeMatrix; \n"
    		  +" uniform mat4 u_InverseBindMatrix; \n"
    		  +"uniform mat4 a_Bone; \n" //bone matrix
    		  + "attribute vec4 a_Position;     \n"		// Per-vertex position information we will pass in.
    		  + "attribute vec4 a_Color;        \n"		// Per-vertex color information we will pass in.
    		  + "attribute vec3 a_Normal;       \n"		// Per-vertex normal information we will pass in.
     
    		  + "varying vec4 v_Color;          \n"		// This will be passed into the fragment shader.
     
    		  + "void main()                    \n" 	// The entry point for our vertex shader.
    		  + "{                              \n"		
    		// Transform the vertex into eye space.
    		  + "   vec3 modelViewVertex = vec3(u_MVMatrix * a_Position);              \n"
    		// Transform the normal's orientation into eye space.
    		  + "   vec3 modelViewNormal = vec3(u_MVMatrix * vec4(a_Normal, 0.0));     \n"
    		// Will be used for attenuation.
    		  + "   float distance = length(u_LightPos - modelViewVertex);             \n"
    		// Get a lighting direction vector from the light to the vertex.
    		  + "   vec3 lightVector = normalize(u_LightPos - modelViewVertex);        \n"
    		// Calculate the dot product of the light vector and vertex normal. If the normal and light vector are
    		// pointing in the same direction then it will get max illumination.
    		  + "   float diffuse = max(dot(modelViewNormal, lightVector), 0.1);       \n" 	  		  													  
    		// Attenuate the light based on distance.
    		  //+ "   diffuse = diffuse * (1.0 / (1.0 + (0.25 * distance * distance))) ;  \n"
    		// Multiply the color by the illumination level. It will be interpolated across the triangle.
    		  + "   v_Color = a_Color * diffuse;                                       \n" 	 
    		// 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 *u_InverseBindMatrix *a_Position; \n"     
    		  + "}                                                                     \n"; 
     
    		return vertexShader;
    	}
    Code :
    	public void onDrawFrame(GL10 glUnused) 
    	{
    GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);			        
     
     
    		GLES20.glUseProgram(mPerVertexProgramHandle);
            // Set program handles for cube drawing.
            mMVPMatrixHandle = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "u_MVPMatrix");
            mMVMatrixHandle = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "u_MVMatrix"); 
            mLightPosHandle = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "u_LightPos");
            mPositionHandle = GLES20.glGetAttribLocation(mPerVertexProgramHandle, "a_Position");
            mColorHandle = GLES20.glGetAttribLocation(mPerVertexProgramHandle, "a_Color");
            mNormalHandle = GLES20.glGetAttribLocation(mPerVertexProgramHandle, "a_Normal"); 
    		mBoneMatHandle = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "a_Bone");
    		BindMatrixHandle = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "u_BindShapeMatrix");
    	 IBMHandle	 = GLES20.glGetUniformLocation(mPerVertexProgramHandle, "u_InverseBindShape");
    //		public int BindMatrixHandle;
    		//mBoneMat = animations[0];
     
    		//mBoneMat ={1, 0, 0, 5, 0, 1, 0, 5, 0 , 0, 1, 0, 0, 0, 0, 1};
            long time = SystemClock.uptimeMillis() % 10000L;
     
     
            LastTime = ThisTime;
            ThisTime = SystemClock.elapsedRealtime();
     
         // ElapsedTime = ThisTime - LastTime;
          GameTime += ThisTime;
     
          RealTime = ThisTime/1000;
     
         // Log.d("Time", Float.toString(ThisTime));
     
        //  for(int i = 0; i<11; i++)
        //  {
        	  for(int j = 0; j<16; j++)
        	  {
        		  CombinedBone[j] = Bone[j] * animations[animCounter][j];
     
     
     
        	  }
        	  animCounter++;
        	  if(animCounter == 11)
        		  animCounter = 0; 
     
        	//  Log.d("Counter", Integer.toString(animCounter));
     
          //}
     
         // Log.d("Time", Float.toString(GameTime));
     
     
     
     
            float angleInDegrees = (360.0f / 10000.0f) * ((int) time);
     
            // Calculate position of the light. Rotate and then push into the distance.
            Matrix.setIdentityM(mLightModelMatrix, 0);
            Matrix.translateM(mLightModelMatrix, 0, 0.0f, 0.0f, -15.0f);      
            Matrix.rotateM(mLightModelMatrix, 0, angleInDegrees, 0.0f, 1.0f, 0.0f);
            Matrix.translateM(mLightModelMatrix, 0,-15.0f, 0.0f, 2.0f);
     
            Matrix.multiplyMV(mLightPosInWorldSpace, 0, mLightModelMatrix, 0, mLightPosInModelSpace, 0);
            Matrix.multiplyMV(mLightPosInEyeSpace, 0, mViewMatrix, 0, mLightPosInWorldSpace, 0);     
     
     
     
    		Matrix.setIdentityM(mModelMatrix, 0);
    		drawCube();
    }
    private void drawCube()
    {
    	mVertices.position(0);		
        GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
        		0, mVertices);        
     
        GLES20.glEnableVertexAttribArray(mPositionHandle);        
     
        // Pass in the color information
        mColors.position(0);
        GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
        		0, mColors);        
     
        GLES20.glEnableVertexAttribArray(mColorHandle);
     
        // Pass in the normal information
        mNormals.position(0);
        GLES20.glVertexAttribPointer(mNormalHandle, mNormalDataSize, GLES20.GL_FLOAT, false, 
        		0, mNormals);
     
        GLES20.glEnableVertexAttribArray(mNormalHandle);
     
    	// 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);
     
      //Matrix.multiplyMM(Bone, 0, controllerMat, 0, Bone,0);
      //Matrix.multiplyMM(Bone, 0, mBindMatrix, 0, Bone, 0);
      GLES20.glUniformMatrix4fv(mBoneMatHandle, 1, false, Identity, 0);
     
    	Matrix.setIdentityM(Identity, 0);
      GLES20.glUniformMatrix4fv(IBMHandle, 1, false, Identity, 0);
      GLES20.glUniformMatrix4fv(BindMatrixHandle, 1, false, mBindMatrix, 0);
        // Pass in the light position in eye space.        
        GLES20.glUniform3f(mLightPosHandle, mLightPosInEyeSpace[0], mLightPosInEyeSpace[1], mLightPosInEyeSpace[2]);
     
        // Draw the cube.
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0,72);   
     
     
     
    }

  4. #4
    Junior Member Newbie
    Join Date
    Apr 2013
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    4
    it wont let me post the full code for some reason. Maybe there is a forbidden word somewhere in it.

  5. #5
    Junior Member Newbie
    Join Date
    Apr 2013
    Posts
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    Of course you can multiply by an Identity matrix. Thep roblem was that my handle was looking for a variable in the shader that wasn't there. Took me 2 weeks to find that error, wow. I see why no one could help me who would look at this crap code and catch that. Thanks for the views anyway.

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