Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>You should be able to use technique of Loop and Blinn in the paper you mentioned. </p> <p>Basically you'll need to offset each control point in the normal direction, both ways, to get the control points for two curves (inner and outer). Then follow the technique in Section 3.1 of Loop and Blinn - this breaks up sections of the curve to avoid triangle overlaps, and then triangulates the main part of the interior (note that this part requires the CPU). Finally, these triangles are filled, and the small curved parts outside of them are rendered on the GPU using Loop and Blinn's technique (at the start and end of Section 3).</p> <p>An alternative technique that may work for you is described here: <a href="https://stackoverflow.com/questions/3076140/thick-bezier-curves-in-opengl">Thick Bezier Curves in OpenGL</a></p> <p>EDIT: Ah, you want to avoid even the CPU triangulation - I should have read more closely.</p> <p>One issue you have is the interface between the geometry shader and the fragment shader - the geometry shader will need to generate primitives (most likely triangles) that are then individually rasterized and filled via the fragment program. </p> <p>In your case with constant thickness I think quite a simple triangulation will work - using Loop and Bling for all the "curved bits". When the two control triangles don't intersect it's easy. When they do, the part outside the intersection is easy. So the only hard part is within the intersection (which should be a triangle).</p> <p>Within the intersection you want to shade a pixel only if both control triangles lead to it being shaded via Loop and Bling. So the fragment shader needs to be able to do texture lookups for both triangles. One can be as standard, and you'll need to add a vec2 varying variable for the second set of texture coordinates, which you'll need to set appropriately for each vertex of the triangle. As well you'll need a uniform "sampler2D" variable for the texture which you can then sample via texture2D. Then you just shade fragments that satisfy the checks for both control triangles (within the intersection).</p> <p>I think this works in every case, but it's possible I've missed something.</p>
    singulars
    1. This table or related slice is empty.
    1. POIs it possible to thicken a quadratic Bézier curve using the GPU only?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USRD1
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. COIt's easy to do if we throw in a little CPU help. Still, I'd rather try to do with with the GPU only. It doesn't _look_ impossible, it just feels like I'm too new to GLSL and graphics in general to complete a solution myself.
      singulars
      1. PO
      1. USzneak
    2. COOh, right. I didn't interpret the "GPU only" too strictly just because the CPU at least needs to be involved in passing the control points.
      singulars
      1. PO
      1. USRD1
    3. COI'd add that if the width is large enough the triangulation is trivial, and even when not it can be pre-calculated. But, I think I see your issue, and I'll edit with an alternative that I think is closer to what you want.
      singulars
      1. PO
      1. USRD1
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload