Скачать или смотреть How to Fix OpenGL Rotation Issues When Handling Mouse Input in 3D Applications

Discover how to properly implement rotation in your 3D models using OpenGL with mouse input, resolving common challenges faced in camera systems.
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This video is based on the question https://stackoverflow.com/q/63418241/ asked by the user 'Abdelbaki Boukerche' ( https://stackoverflow.com/u/12242170/ ) and on the answer https://stackoverflow.com/a/63424476/ provided by the user 'Abdelbaki Boukerche' ( https://stackoverflow.com/u/12242170/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix OpenGL Rotation Issues When Handling Mouse Input in 3D Applications

Are you developing a 3D painting application using OpenGL and struggling with weird rotation results when trying to manipulate your model using mouse input? You’re not alone! Many developers encounter this issue when first implementing rotation with the mouse. Below, we’ll explore the problem in detail and provide a step-by-step guide to fixing it, ensuring smooth and intuitive model rotation as you navigate your artistic creation.

Understanding the Problem

In a 3D application, controlling the rotation of a model with mouse movements is a common feature. However, things can get tricky when you try to rotate around multiple axes simultaneously. The original setup may allow for panning and zooming, but when it comes to rotation, unexpected behavior can occur, resulting in awkward tilting or incorrect axis alignment.

The challenge lies in executing the rotations correctly. In this specific case, when the right mouse button is held down, you want the model to rotate around:

X-axis (Pitch) when the mouse moves up and down.

Y-axis (Yaw) when the mouse moves left and right.

The main problem arises when both rotations are processed at once, leading to undesired visual output.

Our Solution: Separating the Rotations

Upon deeper investigation and advice from fellow developers, the solution became clear: you can only handle one rotation at a time. By separating the rotations for the X and Y axes, we can ensure that the model rotates correctly without unexpected tilting. Let’s go through the steps needed to fix the code.

Step-by-Step Implementation

Set Up Projection and View Matrices: As always, the first step is to set your projection and view matrices properly. This is essential for rendering your 3D scene correctly.

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Initialize the Model Matrix: Create an initial model matrix and set the necessary transformations.

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Handle the X-Axis Rotation: Add the rotation for the X-axis separately from the Y-axis.

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Handle the Y-Axis Rotation: Now add the Y-axis rotation.

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Update the Shader with the Model Matrix: Finally, set the updated model matrix in the shader before rendering the model.

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Revising the Mouse Callback Function

In addition to adjusting the rendering loop, ensure your mouse callback function effectively calculates the rotation angles based on the mouse movement. Make sure that you keep track of the last position of the mouse and compute the offsets correctly.

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Conclusion

By separating the rotations for the X and Y axes, you can effectively control the rotation of your model with the mouse, eliminating the weird tilting issues often encountered. With the right attention to how each axis is processed, you’ll create an intuitive and smooth user experience as you navigate your 3D painting application. Happy coding!