GLSL Geometry Shader Help Needed

[SpiderPig]

I'm currently trying to subdivide a triangle in the geometry shader. I put the material using the shader on a plane made from two triangles.

 

However it seems that the coordinates in GLSL are different to that in Leadwerks? That the positive X axis in Leadwerks is actually the negative X axis in the shader. And the same for the Z axis. The Y axis seems fine.

 

I want the shader to turn the plane of two triangles into a more detailed grid for a terrain. I know the shader works on each triangle, so I will have to divide each triangle itself into the appropriate triangles so that the end result in game looks like a uniform grid.

 

I've thought of tessellation but I don't think it'll give me the results I'm looking for.

 

Any help with this is appreciated. Thanks.

[AggrorJorn]

not sure if this is related but the editor displays in centimeters, in coding you see in meters I believe.

[SpiderPig]

Thanks. I just tried a few things and found I was wrong with the reversed axis's.

 

I'm a little confused still on how to create a vertex in between two original vertices...

[shadmar]

There is an tesselation shader shipped with leadwerks, diffuse+normal+specular+tessellation.shader

[SpiderPig]

Thanks. I'll take a look.

[SpiderPig]

I figured out how to do it now, thanks.

 

It seems that gl_Position doesn't let the shader link when inside a loop that uses a uniform variable as a end condition.

 

int current_level = 0;
uniform int lod_level = 1;
while(current_level < lod_level)
{
current_level++;
gl_Position = pos;
EmitVertex();
}

 

This isn't all the code, but commenting out gl_positon or changing the while loop to;

 

while(current_level < 2)

 

will then work.

[SpiderPig]

Does anyone know how to set a Uniform Buffer Object from c++?

 

The Geometry shader has the following Buffer Object;

layout(std140) uniform DataBlock
{
float terrainHeight[1024];
};

 

https://www.khronos.org/opengl/wiki/Uniform_Buffer_Object

 

Not sure how to get the program ID from a shader in Leadwerks. Or will I have to use OpenGL commands directly?I

 

I figured out how to at least get the Data Blocks index;

 

Shader* sh = material->GetShader();
OpenGLShader* gl_sh = (OpenGLShader*)sh;
unsigned int block_index = glGetUniformBlockIndex(gl_sh->program, "DataBlock");
if (block_index != GL_INVALID_INDEX)
{
//bind it here
}

 

This command gets the size (in bytes) that is available for each buffer;

 

int size;
glGetIntegerv(GL_MAX_UNIFORM_BLOCK_SIZE, &size);

 

In this case it was 65,536 bytes. I think there is a max number of buffers allowed too.

[Ma-Shell]

The material itself has some functions to set shader-uniforms (sadly the function-name does not always reflect this, but e.g. these SetFloat, SetVec2, ... are for setting uniforms)

I don't really know about these types of buffers for shaders but if you can represent your buffer as a texture, you can do the following:

 

C:

m->GetSurface(0)->GetMaterial()->SetTexture("Materials/Developer/window.tex", 3);

This will bind the given texture to texture-slot 3 of m's material.

 

Fragment Shader:

uniform sampler2D texture3;
...
outcolor = texture(texture3, vTexCoords);

 

I haven't tried whether it is possible to access it from the geometry shader, though.

I just tried it in the geometry shader and it works there, as well.

Edited April 11, 2017 by Ma-Shell

[SpiderPig]

Thanks for the help. I think I'll have to do it that way. Buffer Objects aren't big enough for my needs.

[SpiderPig]

I have a problem with the geometry shader I'm working on. If someone could tell me why it works until I un-comment the line,

 

RunLOD(4);

 

That'd be great.

 

The shader, material and a grid model is attached. Thanks.

 

EDIT : Commenting out EmitVertex() solves the linking issue - but why?

 

EDIT : If I'd only looked at the Error log I had hidden to the edge of the screen I would have see this;

 

2: Line 0: Hardware limitation reached, can only emit 60 vertices of this size

 

Well that solves that.