vertexshaderart: rendering issue? vertexCount problem? not sure what to call this

Just started looking at the tutorials, there’s a weird issue with rendering the grid though. Copied your code exactly to be sure I wasn’t doing something silly (though I might still be) - attached an image for you to see - note the bottom left corner… the line is incomplete

screen shot 2017-08-02 at 15 19 14

Seems the vertexCount doesn’t get fed correctly - either of the commented out solutions below work:

void main() {
  float down = floor(sqrt(vertexCount));
  float across = floor(vertexCount/down);
  
  // SOLUTION-1
  //down = floor(sqrt(200.));
  //across = floor(200./down);
  
  // SOLUTION-2
  //float c = 200.;
  //down = floor(sqrt(c));
  //across = floor(c/down);
  
  float x = mod(vertexId, across);
  float y = floor(vertexId / across);
  
  float u = x/(across-1.);
  float v = y/(across-1.);
  
  float ux = u*2.-1.;
  float vy = v*2.-1.;

  gl_Position = vec4(ux, vy, 0.,1.);
  
  gl_PointSize = 10.;
  gl_PointSize *= 20./across;
  gl_PointSize *= resolution.x/600.;
  
  v_color = vec4(1., 0., 0., 1.);

}

Hope this isn’t me being silly and overlooking something - been trying to figure this out for some time now! (actually its probably better if its me and not a bug 😉 )

About this issue

Original URL
State: open
Created 7 years ago
Comments: 16 (8 by maintainers)

Most upvoted comments

I see the GL_ES wrapper as including C/C++ in my JavaScript.

I wouldn’t do this

// int main(int argc, const char* argv[]) {
//   .. 
//  ..
// }

function main() {
   ...
   ...

}

So similarly I don’t put non-WebGL in my WebGL shaders. It’s misleading IMO to most WebGL devs who are unlikely to ever touch OpenGL (there’s several orders of magnitude more JS programmers than C/C++ programmers) so rather than clutter my code with stuff they’ll never use I try to keep it as clean as possible.

It gets worse in WebGL2. The first line of the shader must be

#version 300 es

And there is no way to #if it out for desktop. Since It’s going to have to be a WebGL only shader then I keep the non-WebGL stuff out.

but of course you’re free to do whatever you want, just explaining my reasoning.

greggman on Aug 8, 2017