Here’s my issue: I’m looking to detect shadow in a picture. It so happens that I have a three-dimensional object of the scene (obtained through stereo method) and I’m trying to assess if shadow mapping is a sensible method to find the shadow in the picture. For this I’m trying to use openGL as I think it’s probably the most optimized solution out there. My objective is to output a 2D binary image corresponding to the shadow map from the camera point of view. I have everything I need, I can render the scene in 3D without issues but I do not know where to get the shadow map from and to output it as a binary mask.
If you have any input, I would greatly appreciate it,
Hi Carmine, thanks for your reply! I have a 3D image. I place the light source and then render the scene from a given point of view (different from the light source). This naturally leads to shadows appearing in the scene and I want to extract these shadows as a 2D binary mask as seen from the point of view. Nothing really fancy here, and I am pretty sure it must be straightforward for a seasoned openGL programmer but I can’t find any info as to where and how I can extract this.
Don’t have an easy answer for you. I’ve implemented OpenGL shadowing using the shadow mapping approach. My code was based on examples I found on the web. The basic idea is easy to understand, but the OpenGL implementation was hard for me to follow on a line-by-line level. So I’m not the one to give advice on this topic. You could try what I did by looking at examples of shadowing code on the web until you find one that made enough sense to use as a template.
sounds to me like you are missing the basic idea of how to do it …
maybe just to get you started, a little easy help:
Thanks for your replies guys. uwi2k2, I understand the principle fairly well, I have implemented the algorithm in Matlab and can obtain the result I want there. I want to use openGL for efficiency (speed GPU + better precision). I am just trying to locate/extract (or how to create) the two-dimensional shadow-map of the scene as seen from the camera point of view. And I am having trouble finding where/how it is stored by openGL.
Shadow mapping is quite an advanced technique for a beginner and will require you to learn most aspects of ‘modern’ OpenGL (shaders, textures, FBOs). There’s lots of good tutorials on the internet, but I would recommend learnopengl.com for its clarity, and it includes a page about shadow mapping as well.