GlTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP) Texture properties may be: glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP) Without modification, the scalars of a texture coord range from 0.0 to 1.0. Similar to 1, but with calculations in the fragment shader to check, whether the texture coords are within the border area, instead of the texture border. I've never used a color border for a single channel texture, so this approach needs to be verified.

GlTexParameterfv(GL_TEXTURE_2D,GL_TEXTURE_BORDER_COLOR,borderColor4f) GlTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_BORDER) Texture properties: glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_BORDER)

Set the texture border property (single 4 component color), there will be no need to do extra fragment shader calculations, the texture unit/sampler does all the work.

This way, no extra geometry or draw calls are required.

Draw the rectangle as big as the image + border will be and adjust texture coords for the image, so that it will be placed within the rectangle appropriately.

If you want a 'line border', you cannot do anything else than drawing the image triangles/quads (GL_TRIANGLES,GL_QUADS), and in an additional call the outline (using GL_LINES), where you may share the vertices of a single quad.Ĭonsider, that lines can't be drawn efficiently by many GPU's) To get the pixel shader drawing something, there needs to be geometry.Īs far as I understand, you want to draw a border around these images,īut the outermost fragments generated would be image pixels in a basic implementation, It doesn't work for concave objects of course but depending on your quality needs may be 'good enough' If it is between: -epsilon < 0 < epsilonĤ) Use cheap-o-rama object scaling.

In the vertex shader check the dot product of the normal with the view. Draw & Blend the texture image back into the framebufferĢ) Pass along extra vertex, namely which vertices are adjacent in the proper winding order, and dynamically generate extra outline triangles.ģ) Use cheap edge detection.Do a N-pass 'tap', such as 5 or 7 pass tap where you blur the texture via rendering to itself in both the vertical and horizontal direction (another option is to scale drawing the texture image up).The common search terms are:ġ) The traditional approach is to use the stencil buffer and render to textureĬlear the stencil buffer (usually done once per frame) glClear( GL_COLOR_BUFFER_BIT | DEPTH_BUFFER_BIT | STENCIL_BUFFER_BIT )ĭisable Color Buffer Writes glColorMask( 0, 0, 0, 0 ) Įnable the Stencil buffer Set stencil to always pass and replace glStencilOp( GL_KEEP, GL_KEEP, GL_REPLACE ) There are a couple of ways of doing this depending on the a) Qaulity, and b) Speed you need.

Opengl only use es 2.0 calls