How to add glowing effect to a line for OpenGL? [closed]

Question

How can I add a glowing effect to a line that I draw? I'm using OpenGL for Linux.

Cussedness

This is commonly called "adding bloom", to aid in your search. There is a nice section in how to do it here – Unreconstructed

There is also a great summary of glow effects here – Unreconstructed

Answer 1

You can implement the radial blur effect described on Nehe Lesson 36. The main idea is to render the drawing to a texture, and do that N times with a small offset after each render, until the drawing is ready to be copied to the framebuffer.

I've written a small demo that uses Qt and OpenGL. You can see the original drawing (without the blur) below:

The next image shows the drawing with the blur effect turned on:

I know it's not much, but it's a start.

Moya

I wasn't able to edit the answer, but I think the correct path has been changed to github.com/karlphillip/GraphicsProgramming/tree/master/… – Condensate

Answer 2

I too once hoped there was a very simple solution to this, but unfortunately it is a little complicated, at least for a beginner.

The way glowing effects are implemented today, regardless of API (D3D,OpenGL) is with pixel/fragment-shaders. It usually involves multiple render passes where you render your scene, then render a pass where only "glowing objects" are visible, then you apply a bloom pixelshader and compose them together.

See the link provided by @Valmond for details

Edit:

It should be added that this can be achieved with deferred rendering, where normals, positions and other information like a "glow flag" is rendered to a texture, i.e. stored in different components of the texture. Then a shader will read from the textures and do lightning computations and post-processing effects in a single pass since all data it needs is available from that rendered texture.

Reseda

Answer 3

Check this out : http://developer.download.nvidia.com/books/HTML/gpugems/gpugems_ch21.html

It explains easily how to make glow effects.

Sandfly

That really doesn't explain much about how to do it. It just talks about the process and not the actual implementation – Pegg

Answer 4

Without using shaders, you might also try rendering to texture and doing a radial blur. As a starting point check out NeHe-Tutorials.

Bilateral