Posted by imakerobots on May 28, 2023; 1:24am
URL: https://forum.jogamp.org/How-do-I-use-stencil-textures-for-outlining-shapes-tp4042652.html

Hello, everyone!  I hope you're all doing well.

After 20 years of graphics I finally jump from fixed-function to programmable pipeline.

In my existing project (https://github.com/MarginallyClever/Robot-Overlord-App/) I am using a stencil buffer and an offset-by-normal fragment shader to highlight selected objects.  Works great, doesn't look very good, as described with pics in https://github.com/MarginallyClever/Robot-Overlord-App/issues/138

Having read https://open.gl/depthstencils and https://alexanderameye.github.io/notes/rendering-outlines/ I'd like to use the Jump Flood Algorithm to make really nice outlines.  I also found https://github.com/kiwipxl/GLSL-shaders/blob/master/outline.glsl

Currently I am using the jogamp-fat 2.4.0.  I think this was done so that the natives could be repacked for distribution correctly?  It's been a long time.  In practical terms it means that I can't access a bunch of internal texture formats like GL_STENCIL_INDEX8 or GL_DEPTH24_STENCIL8 because

> Caught GLException: format 0x8d48 not supported [yet], pls notify the maintainer in case this is our bug.

My project is large so I have tried to write some smaller tests.  You can find them in branch https://github.com/MarginallyClever/Robot-Overlord-App/tree/new-outline at
com/marginallyclever/robotoverlord/renderpanel/OpenGLTestOrthographic.java
extended to com/marginallyclever/robotoverlord/renderpanel/OpenGLTestPerspective.java
extended to com/marginallyclever/robotoverlord/renderpanel/OpenGLTestStencil.java

the last one is the item I'm trying to make work.  At this stage all I'm trying to do is display the contents of the stencil texture before I move on to tackling JFA.

I have tried to attach RenderDoc.  I must still have some active FF in there because it flatly refuses to work with me.

What I'm looking for, please, is a tutorial/demo that draws a single triangle in ortho projection, captures the stencil to texture, runs JFA, and outlines the triangle.  I feel confident if I had one working model I could carry the ball the rest of the way.  GL3 would be awesome, GL4 also works.

Thank you!