C#•7mo ago

Frustum culling

Hello i try to setup a Frustum culling system but it always returns true even if the object is not in the frustum. What i guess it is: Before normalization, it functions correctly, albeit with an incorrect size. To achieve precision, I must closely inspect my object, making slight rotations. However, after normalization, it consistently returns true and never provides a false outcome. Normalized: https://media.discordapp.net/attachments/1036008388552839169/1173215015948521573/image.png?ex=656324a1&is=6550afa1&hm=7de8eef894c9cf4cb5be82363e2ee0c06aa89034da866294b7d0da3dbc8ce1d4&= Wihout Normalizing: if i look exactly on it i can see it: https://cdn.discordapp.com/attachments/1036008388552839169/1173215314331320440/image.png?ex=656324e8&is=6550afe8&hm=8bf65ae87f380c572e57db16235cfa9e02d8cc827433beea3cf2dc81af6f577b& But if i move more away it is gone: https://cdn.discordapp.com/attachments/1036008388552839169/1173215337727139890/image.png?ex=656324ed&is=6550afed&hm=64e388f63e55102dda61e83af167daf05b5d8bb4fa258eb9dfea8c73362c0193& My class:

public class Frustum {
    
    // View frustum planes
    private Plane[] _frustumPlanes;

    public Frustum(Matrix4x4 viewProjectionMatrix) {
        _frustumPlanes = ExtractPlanes(viewProjectionMatrix);
    }

    public bool IsSphereInFrustum(Vector3 center, float radius) {
        foreach (var plane in _frustumPlanes) {
            float distance = Vector3.Dot(plane.Normal, center) + plane.D;

            if (distance < -radius) {
                // The sphere is entirely behind this plane, it is outside the frustum
                return false;
            }
        }

        // The sphere is not entirely behind any plane, it is partially or fully inside the frustum
        return true;
    }

    private Plane[] ExtractPlanes(Matrix4x4 viewProjectionMatrix) {
        
        // Extract view frustum planes from the view-projection matrix
        Plane[] planes = new Plane[6];

        // Left plane
        planes[0] = new Plane(
            viewProjectionMatrix.M14 + viewProjectionMatrix.M11,
            viewProjectionMatrix.M24 + viewProjectionMatrix.M21,
            viewProjectionMatrix.M34 + viewProjectionMatrix.M31,
            viewProjectionMatrix.M44 + viewProjectionMatrix.M41
        );

        // Right plane
        planes[1] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M11,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M21,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M31,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M41
        );

        // Bottom plane
        planes[2] = new Plane(
            viewProjectionMatrix.M14 + viewProjectionMatrix.M12,
            viewProjectionMatrix.M24 + viewProjectionMatrix.M22,
            viewProjectionMatrix.M34 + viewProjectionMatrix.M32,
            viewProjectionMatrix.M44 + viewProjectionMatrix.M42
        );

        // Top plane
        planes[3] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M12,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M22,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M32,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M42
        );

        // Near plane
        planes[4] = new Plane(
            viewProjectionMatrix.M13,
            viewProjectionMatrix.M23,
            viewProjectionMatrix.M33,
            viewProjectionMatrix.M43
        );

        // Far plane
        planes[5] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M13,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M23,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M33,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M43
        );

        // Normalize the planes
        for (int i = 0; i < 6; i++) {
            planes[i] = Plane.Normalize(planes[i]);
        }
        
        return planes;
    }
}

public class Frustum {
    
    // View frustum planes
    private Plane[] _frustumPlanes;

    public Frustum(Matrix4x4 viewProjectionMatrix) {
        _frustumPlanes = ExtractPlanes(viewProjectionMatrix);
    }

    public bool IsSphereInFrustum(Vector3 center, float radius) {
        foreach (var plane in _frustumPlanes) {
            float distance = Vector3.Dot(plane.Normal, center) + plane.D;

            if (distance < -radius) {
                // The sphere is entirely behind this plane, it is outside the frustum
                return false;
            }
        }

        // The sphere is not entirely behind any plane, it is partially or fully inside the frustum
        return true;
    }

    private Plane[] ExtractPlanes(Matrix4x4 viewProjectionMatrix) {
        
        // Extract view frustum planes from the view-projection matrix
        Plane[] planes = new Plane[6];

        // Left plane
        planes[0] = new Plane(
            viewProjectionMatrix.M14 + viewProjectionMatrix.M11,
            viewProjectionMatrix.M24 + viewProjectionMatrix.M21,
            viewProjectionMatrix.M34 + viewProjectionMatrix.M31,
            viewProjectionMatrix.M44 + viewProjectionMatrix.M41
        );

        // Right plane
        planes[1] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M11,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M21,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M31,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M41
        );

        // Bottom plane
        planes[2] = new Plane(
            viewProjectionMatrix.M14 + viewProjectionMatrix.M12,
            viewProjectionMatrix.M24 + viewProjectionMatrix.M22,
            viewProjectionMatrix.M34 + viewProjectionMatrix.M32,
            viewProjectionMatrix.M44 + viewProjectionMatrix.M42
        );

        // Top plane
        planes[3] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M12,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M22,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M32,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M42
        );

        // Near plane
        planes[4] = new Plane(
            viewProjectionMatrix.M13,
            viewProjectionMatrix.M23,
            viewProjectionMatrix.M33,
            viewProjectionMatrix.M43
        );

        // Far plane
        planes[5] = new Plane(
            viewProjectionMatrix.M14 - viewProjectionMatrix.M13,
            viewProjectionMatrix.M24 - viewProjectionMatrix.M23,
            viewProjectionMatrix.M34 - viewProjectionMatrix.M33,
            viewProjectionMatrix.M44 - viewProjectionMatrix.M43
        );

        // Normalize the planes
        for (int i = 0; i < 6; i++) {
            planes[i] = Plane.Normalize(planes[i]);
        }
        
        return planes;
    }
}

3 Replies

MrScautHD•7mo ago

Has anyone a idea?

WEIRD FLEX•7mo ago

did you debug it do look if numbers are what you expect? to me the -radius in if (distance < -radius) { seems odd

MrScautHD•7mo ago

i got it already thx:

        Matrix4x4 viewProjection = Matrix4x4.Transpose(Rlgl.GetMatrixModelview()) * Matrix4x4.Transpose(Rlgl.GetMatrixProjection());

        Matrix4x4 viewProjection = Matrix4x4.Transpose(Rlgl.GetMatrixModelview()) * Matrix4x4.Transpose(Rlgl.GetMatrixProjection());

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Frustum culling