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How to detect a screen in a photo

Is there a way to make a difference between a photo of an actual object and a photo of an object through a computer or smartphone screen. For example: how can I detect that the second image is taken from a screen? Thank you very much!
Hugo
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Constructing base mesh for required subdivision surface

Given a triangle mesh, does there exist any algorithm to compute a base mesh (smaller in size than the triangle mesh) that could be subdivided multiple times to get back the original mesh (or an approximate of the original) ? Thanks!
xperien
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Double rasterization work on triangles edges.

I know that fragments are rasterized in a 2x2 quad. That's why the seam between two triangles can be rasterized twice. At least that article states this. I wonder is it still true today on modern hardware?
nikitablack
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What is causing this odd scaling behavior?

OK so I have a simple setup going on. Basically I am just drawing some textures and shapes. However sizing is going weird... let me show you how any maybe you can diagnose. Basically everything is broken into components that work fine by…
J.Doe
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Interlacing vertex buffer data with extra efficiency

I am making a 2d game in opengl es 2.0 Inside are tons of rectangles defined by 4 points and one 4 component color. I am using vertex buffer objects, and I have heard that it is efficent to interlace the data. So like traditionally you would…
J.Doe
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Unwinding an image on a spiral to make it long and flat

Here's an odd intellectual puzzle. Something I was daydreaming about on a train - but the maths are somewhat beyond me. How would someone go about un-winding a spiral to produce a long flat image? Like a rope on a spool, I'd want to uncoil the…
headbanger
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Calculate vanishing point

In perspective projection, group of parallel lines have the same vanishing point. I am interesting about the reverse calculation: Getting the group of parallel lines equations that their vanishing point specific point. Say I know that the camera is…
Raz Halaly
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3D rotation matrix around vector

I am using matrix for performing 3D rotations. I know that in 3D space the matrix product order is important - changing the order of the matrices can effect the rotate result. So I am interesting about how can I create a rotate matrix that perform…
Raz Halaly
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Bilinear Transformation not working

I implemented this algorithm to fit given image to specified quadrilateral but the output is blank. I implemented it in C# as follows Bitmap inputImage = new Bitmap("D:\\Image\\A2.jpg"); Bitmap outputBitmap = new Bitmap(inputImage.Width,…
Sandiip
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How are hard and soft shadows cast?

I have been studying computer graphics, from the book Fundamentals of Computer Graphic (but the third edition), and I lastly read about texture mapping and shadow maps. Though, I didn't exactly understand how they function. I know there is also…
phong
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Finding the maximum number of disconnected fragments

In a plane, we have a convex polygon with n sides. What would be the maximum number of disconnected pieces / fragments if this polygon is clipped against a square?
Sharmishtha
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Affine Transformation

We have a matrix $$\begin{bmatrix} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33} \end{bmatrix}$$ This matrix represents a transformation in homogeneous coordinates. My question is whether the above matrix is…
Sharmishtha
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Line segments overlapping

I have implemented line segments intersetion test and at the very same test I want to include the fact that if two line segments overlap each other partially or fully , it will be flagged as no intersection. Some hint to it would be great to have!
sajis997
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Can't render multiple VAO's?

I'm a newbie to OpenGL and I was following a series by "thebennybox" on Youtube. Specifically his series on modern opengl programming. I thought I would try to implement his Mesh wrapper using the vector in C++ rather than using arrays of data and…
Jonathon Blow
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How to blend World Space Normals

I am trying to blend two world space normals inside a shader. One comes from a tangent space normal map converted into world space using a classic TBN matrix and the other one is a mesh normal map in world space. I found some interesting resources…
MaT
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