Why is My OpenGL Normal Mapping Producing Incorrect Results?

Normal Mapping Gone Awry: A Solution

As the issue suggests, the implementation of normal mapping in an OpenGL application is facing anomalies. Upon scrutinizing the code, we have identified several potential causes for the incorrect results.

Vertex Tangent and Bitangent Calculation

The function you provided for calculating the tangent and bitangent vectors may be prone to errors. It's recommended to use a robust method such as the one described in the following paper: [Calculating Tangent Space Basis Vectors for Mesh]()[1]

Fragment Shader Implementation

Your fragment shader contains issues that could contribute to the incorrect rendering:

• Multiple Color Assignments: The color variable is set multiple times within the shader. This behavior can cause unexpected blending or overwriting of colors.
• Incorrect Color Modification: Instead of modifying the fragment color by adding intensities, you should use color multiplication for lighting calculations.
• Non-Ambient and Non-Diffuse Components: Currently, the fragment shader lacks ambient and diffuse lighting components. Adding these components can significantly enhance the overall appearance.

Additional Considerations

Beyond the shader issues, there are a few other aspects to consider:

• Accurate Normal Map: Ensure that the normal map used is of high quality and correctly calibrated.
• Tangent Space Transformation: Verify that the TBN matrix is correctly calculated and applied in the vertex shader.
• Model Orientation: Check if the model is positioned and oriented correctly within the scene.

Tips for Troubleshooting

• Enable Debug Mode: If available, switch to debug mode for your graphics driver to receive more detailed error messages.
• Inspect Shader Logs: Examine the compilation and runtime logs of your shaders to identify any potential errors or warnings.
• Visualize TBN Vectors: Draw colored lines to visualize the TBN vectors at each vertex position to ensure they align with the object's surface.
• Simplify Shader: Start with a simplified shader that only includes essential components, then gradually add complexity as needed.
• Seek Assistance: If you encounter persistent issues, don't hesitate to seek help from online forums or documentations.

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