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KaiserJohan

OpenGL CSM do these depth textures look correct?

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I'm troubleshooting cascaded shadow mapping for DX11. I need some input, if the depth textures I generated for the different cascades are correct.

 

Here's the scene, where you see shadow artifacts from the directional light (looking (-1, -1, -1) - using right-handed coordinate system). Ignore the point light which is casting shadows near the cube.

 

[attachment=23212:scene.png]

 

And here are the various cascade depth textures, in the following ranges: [0.1, 6], [6, 12], [12, 18], [18, 100]

 

[attachment=23213:csm1.png]

 

[attachment=23214:csm2.png]

 

[attachment=23215:csm3.png]

 

[attachment=23217:csm4.png]

 

But that cant be right now that I think about it - for example, the alien is 6 units into the scene from cameras POV, so it should be clipped in the third image for example?

 

The way I am creating the view-Projection matrix for this is using the code I used in OpenGL, and I am using the same math library so the matrices should be 1-to-1.

    CameraFrustrum CalculateCameraFrustrum(const float fovDegrees, const float aspectRatio, const float minDist, const float maxDist, const Mat4& cameraViewMatrix)
    {
        CameraFrustrum ret = { Vec4(1.0f, 1.0f, -1.0f, 1.0f), Vec4(1.0f, -1.0f, -1.0f, 1.0f), Vec4(-1.0f, -1.0f, -1.0f, 1.0f), Vec4(-1.0f, 1.0f, -1.0f, 1.0f),
                               Vec4(1.0f, -1.0f, 1.0f, 1.0f), Vec4(1.0f, 1.0f, 1.0f, 1.0f), Vec4(-1.0f, 1.0f, 1.0f, 1.0f), Vec4(-1.0f, -1.0f, 1.0f, 1.0f), };

        const Mat4 perspectiveMatrix = PerspectiveMatrixFov(fovDegrees, aspectRatio, minDist, maxDist);
        const Mat4 invMVP = glm::inverse(perspectiveMatrix * cameraViewMatrix);

        for (Vec4& corner : ret)
        {
            corner = invMVP * corner;
            corner /= corner.w;
        }

        return ret;
    }

    Mat4 CreateDirLightVPMatrix(const CameraFrustrum& cameraFrustrum, const Vec3& lightDir)
    {
        Mat4 lightViewMatrix = glm::lookAt(Vec3(0.0f), -glm::normalize(lightDir), Vec3(0.0f, -1.0f, 0.0f));

        Vec4 transf = lightViewMatrix * cameraFrustrum[0];
        float maxZ = transf.z, minZ = transf.z;
        float maxX = transf.x, minX = transf.x;
        float maxY = transf.y, minY = transf.y;
        for (uint32_t i = 1; i < 8; i++)
        {
            transf = lightViewMatrix * cameraFrustrum[i];

            if (transf.z > maxZ) maxZ = transf.z;
            if (transf.z < minZ) minZ = transf.z;
            if (transf.x > maxX) maxX = transf.x;
            if (transf.x < minX) minX = transf.x;
            if (transf.y > maxY) maxY = transf.y;
            if (transf.y < minY) minY = transf.y;
        }

        Mat4 viewMatrix(lightViewMatrix);
        viewMatrix[3][0] = -(minX + maxX) * 0.5f;
        viewMatrix[3][1] = -(minY + maxY) * 0.5f;
        viewMatrix[3][2] = -(minZ + maxZ) * 0.5f;
        viewMatrix[0][3] = 0.0f;
        viewMatrix[1][3] = 0.0f;
        viewMatrix[2][3] = 0.0f;
        viewMatrix[3][3] = 1.0f;

        Vec3 halfExtents((maxX - minX) * 0.5, (maxY - minY) * 0.5, (maxZ - minZ) * 0.5);

        return OrthographicMatrix(-halfExtents.x, halfExtents.x, -halfExtents.y, halfExtents.y, halfExtents.z, -halfExtents.z) * viewMatrix;
    }
Edited by KaiserJohan

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you may try to render the cascade itself, it would be easier to debug.

Once you got the view-projection matrix of your shadow cascade, you can find all 8 vertex of the frustum in world space using the inverse view_projection matrix, than you can visualize the cascade.

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