Trying to write shader with lines from OBJ file about glslviewer

[snibbe]

I'll use the workaround. Thanks for such a quick answer!

[patriciogonzalezvivo]

I found this example, is slightly different because it encode the direction that the vertex needs to take on the a_normal vertex attribute.

shader.vert

#ifdef GL_ES
precision mediump float;
#endif

uniform mat4    u_projectionViewMatrix;

uniform float   u_radius;
uniform float   u_width;

attribute vec4  a_position;
attribute vec4  a_color;
attribute vec3  a_normal;
attribute vec2  a_texcoord;

varying vec4    v_position;
varying vec4    v_color;
varying vec2    v_texcoord;

void main() {
    v_texcoord = a_texcoord;
    v_position = a_position;
    v_color = a_color;
 
    v_position.xyz += a_normal * u_width;

    gl_Position = u_projectionViewMatrix * v_position;
}

[patriciogonzalezvivo]

Hi @snibbe! So happy and honored seeing you here! Just send you a quick mail, this is one of those cases. GlslViewer geometry loaders mostly know to work with points and triangles at the moment. I usually work with lines them by creating collapsed geometry composed of triangles.
The trick require:

• creating a spline (a line constructed of triangles). where each pair of vertices at each side of the spline is send to the same position.
• using the a_texcoord attribute then I extrude it dynamically on the vertex shader.

I know a bit convoluted.
I will try to bring supporting for them when I have some time.

[snibbe]

If you happen to have an example vertex shader that does this, I would be very grateful if you posted it here. The solution I just tried uses gl_VertexID, but for some reason the glsl version on my Mac in glsViewer is limited to 1.2 and doesn't support gl_VertexID.