# OpenGL Speckles on models at far distances

## Recommended Posts

Shawn619    342

I get these weird speckles on my model when using a shader and rendering the model at far distances. You can see this if you look closely at the triangles rendered closer to the sun(light) and triangles render further from the sun. Anyone know what this phenomena is called? And possible how to fix it in opengl?

##### Share on other sites
deftware    1778

Maybe z-fighting? How is your geometry organized? How are you generating it? What is the 'box' around everything?...and lastly, out of sheer curiousity, why is everything green?

##### Share on other sites
Shawn619    342

Maybe z-fighting? How is your geometry organized? How are you generating it? What is the 'box' around everything?...and lastly, out of sheer curiousity, why is everything green?

There's nothing technical behind coloring everything green. Green is supposed to represent a forest terrain, it reminds me of final fantasy, specifically ff tactics.

But I import all models through a .obj importer that is like this one, except I changed it to save all verts,normals,faces and not discards them after saving the model to a display list, then wrapped it in a class:



{

std::vector<std::string*> coord;        //read every single line of the obj file as a string

std::vector<coordinate*> vertex;

std::vector<face*> faces;

std::vector<coordinate*> normals;       //normal vectors for every face

std::ifstream in(filename);     //open the .obj file

if(!in.is_open())       //if not opened, exit with -1

{

std::cout << "Nor oepened" << std::endl;

return -1;

}

char buf[256];

//read in every line to coord

while(!in.eof())

{

in.getline(buf,256);

coord.push_back(new std::string(buf));

}

//go through all of the elements of coord, and decide what kind of element is that

for(int i=0;i<coord.size();i++)

{

if(coord[i]->c_str()[0]=='#')   //if it is a comment (the first character is #)

continue;       //we don't care about that

else if(coord[i]->c_str()[0]=='v' && coord[i]->c_str()[1]==' ') //if vector

{

float tmpx,tmpy,tmpz;

sscanf(coord[i]->c_str(),"v %f %f %f",&tmpx,&tmpy,&tmpz);       //read in the 3 float coordinate to tmpx,tmpy,tmpz

vertex.push_back(new coordinate(tmpx,tmpy,tmpz));       //and then add it to the end of our vertex list

}else if(coord[i]->c_str()[0]=='v' && coord[i]->c_str()[1]=='n')        //if normal vector

{

float tmpx,tmpy,tmpz;   //do the same thing

sscanf(coord[i]->c_str(),"vn %f %f %f",&tmpx,&tmpy,&tmpz);

normals.push_back(new coordinate(tmpx,tmpy,tmpz));

}else if(coord[i]->c_str()[0]=='f')     //if face

{

int a,b,c,d,e;

if(count(coord[i]->begin(),coord[i]->end(),' ')==3)     //if it is a triangle (it has 3 space in it)

{

sscanf(coord[i]->c_str(),"f %d//%d %d//%d %d//%d",&a,&b,&c,&b,&d,&b);

faces.push_back(new face(b,a,c,d));     //read in, and add to the end of the face list

}else{

sscanf(coord[i]->c_str(),"f %d//%d %d//%d %d//%d %d//%d",&a,&b,&c,&b,&d,&b,&e,&b);

faces.push_back(new face(b,a,c,d,e));   //do the same, except we call another constructor, and we use different pattern

}

}

}

//raw

int num;        //the id for the list

num=glGenLists(1);      //generate a uniqe

glNewList(num,GL_COMPILE);      //and create it

for(int i=0;i<faces.size();i++)

{

{

//basically all I do here, is use the facenum (so the number of the face) as an index for the normal, so the 1st normal owe to the first face

//I subtract 1 because the index start from 0 in C++

glNormal3f(normals[faces[i]->facenum-1]->x,normals[faces[i]->facenum-1]->y,normals[faces[i]->facenum-1]->z);

//draw the faces

glVertex3f(vertex[faces[i]->faces[0]-1]->x,vertex[faces[i]->faces[0]-1]->y,vertex[faces[i]->faces[0]-1]->z);

glVertex3f(vertex[faces[i]->faces[1]-1]->x,vertex[faces[i]->faces[1]-1]->y,vertex[faces[i]->faces[1]-1]->z);

glVertex3f(vertex[faces[i]->faces[2]-1]->x,vertex[faces[i]->faces[2]-1]->y,vertex[faces[i]->faces[2]-1]->z);

glVertex3f(vertex[faces[i]->faces[3]-1]->x,vertex[faces[i]->faces[3]-1]->y,vertex[faces[i]->faces[3]-1]->z);

glEnd();

}else{

glBegin(GL_TRIANGLES);

glNormal3f(normals[faces[i]->facenum-1]->x,normals[faces[i]->facenum-1]->y,normals[faces[i]->facenum-1]->z);

glVertex3f(vertex[faces[i]->faces[0]-1]->x,vertex[faces[i]->faces[0]-1]->y,vertex[faces[i]->faces[0]-1]->z);

glVertex3f(vertex[faces[i]->faces[1]-1]->x,vertex[faces[i]->faces[1]-1]->y,vertex[faces[i]->faces[1]-1]->z);

glVertex3f(vertex[faces[i]->faces[2]-1]->x,vertex[faces[i]->faces[2]-1]->y,vertex[faces[i]->faces[2]-1]->z);

glEnd();

}

}

glEndList();

//delete everything to avoid memory leaks

for(int i=0;i<coord.size();i++)

delete coord[i];

for(int i=0;i<faces.size();i++)

delete faces[i];

for(int i=0;i<normals.size();i++)

delete normals[i];

for(int i=0;i<vertex.size();i++)

delete vertex[i];

return num;     //return with the id

}



?

?

?

?

?

?

?

The green box is just a couple of plain quads that house my scene.

?

Edited by Shawn619

##### Share on other sites

There's not enough info to go on. Are you using a shader? If so, did you remember to make sure everything is intialized first? It could be that the geometry is duplicated and this would cause the z-fighting artifacts that radioteeth mentioned.

##### Share on other sites
Shawn619    342

My drawing goes like this:

//globals

//init
//end init

//drawing per frame

//draw scene
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, windowWidth, windowHeight);
glClearColor(0,0.5,0.5,0);
glMatrixMode(GL_PROJECTION);
gluPerspective(60.0, (float)windowWidth / (float)windowHeight, 0.4, 9000.0);
glMatrixMode(GL_MODELVIEW);

//enables/disables
glEnable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

//set camera
gluLookAt(cam.posX,cam.posY,cam.posZ,cam.viewX,cam.viewY,cam.viewZ,cam.upX,cam.upY,cam.upZ);

//draw calls
//...

glUseProgram(0);

glutSwapBuffers();

//end drawing per frame


?

?

?

Edited by Shawn619

Shawn619    342

Any ideas?

##### Share on other sites
Shawn619    342

Solved!

Very unusual problem, which is why I couldn't fine many similar problem on google.

I narrowed the problem down to the attenuation calculated in my glsl shader. Funnily enough, my attenuation calculations were fine. The problem was solved by changing:

if( gl_FrontFacing ){
//color = ambient and diffuse with attenuation
}else{
//color = only ambient
}



to

if( diffuseTerm > 0.0){
//color = ambient and diffuse with attenuation
}else{
//color = only ambient
}


I don't know how, but there was a problem with gl_FrontFacing.

Edited by Shawn619

## Create an account

Register a new account

• ### Similar Content

• By Zaphyk
I am developing my engine using the OpenGL 3.3 compatibility profile. It runs as expected on my NVIDIA card and on my Intel Card however when I tried it on an AMD setup it ran 3 times worse than on the other setups. Could this be a AMD driver thing or is this probably a problem with my OGL code? Could a different code standard create such bad performance?

• I'm trying to get some legacy OpenGL code to run with a shader pipeline,
The legacy code uses glVertexPointer(), glColorPointer(), glNormalPointer() and glTexCoordPointer() to supply the vertex information.
I know that it should be using setVertexAttribPointer() etc to clearly define the layout but that is not an option right now since the legacy code can't be modified to that extent.
I've got a version 330 vertex shader to somewhat work:
#version 330 uniform mat4 osg_ModelViewProjectionMatrix; uniform mat4 osg_ModelViewMatrix; layout(location = 0) in vec4 Vertex; layout(location = 2) in vec4 Normal; // Velocity layout(location = 3) in vec3 TexCoord; // TODO: is this the right layout location? out VertexData { vec4 color; vec3 velocity; float size; } VertexOut; void main(void) { vec4 p0 = Vertex; vec4 p1 = Vertex + vec4(Normal.x, Normal.y, Normal.z, 0.0f); vec3 velocity = (osg_ModelViewProjectionMatrix * p1 - osg_ModelViewProjectionMatrix * p0).xyz; VertexOut.velocity = velocity; VertexOut.size = TexCoord.y; gl_Position = osg_ModelViewMatrix * Vertex; } What works is the Vertex and Normal information that the legacy C++ OpenGL code seem to provide in layout location 0 and 2. This is fine.
What I'm not getting to work is the TexCoord information that is supplied by a glTexCoordPointer() call in C++.
Question:
What layout location is the old standard pipeline using for glTexCoordPointer()? Or is this undefined?

Side note: I'm trying to get an OpenSceneGraph 3.4.0 particle system to use custom vertex, geometry and fragment shaders for rendering the particles.

• Hi i am new to this forum  i wanted to ask for help from all of you i want to generate real time terrain using a 32 bit heightmap i am good at c++ and have started learning Opengl as i am very interested in making landscapes in opengl i have looked around the internet for help about this topic but i am not getting the hang of the concepts and what they are doing can some here suggests me some good resources for making terrain engine please for example like tutorials,books etc so that i can understand the whole concept of terrain generation.

• By KarimIO
Hey guys. I'm trying to get my application to work on my Nvidia GTX 970 desktop. It currently works on my Intel HD 3000 laptop, but on the desktop, every bind textures specifically from framebuffers, I get half a second of lag. This is done 4 times as I have three RGBA textures and one depth 32F buffer. I tried to use debugging software for the first time - RenderDoc only shows SwapBuffers() and no OGL calls, while Nvidia Nsight crashes upon execution, so neither are helpful. Without binding it runs regularly. This does not happen with non-framebuffer binds.
GLFramebuffer::GLFramebuffer(FramebufferCreateInfo createInfo) { glGenFramebuffers(1, &fbo); glBindFramebuffer(GL_FRAMEBUFFER, fbo); textures = new GLuint[createInfo.numColorTargets]; glGenTextures(createInfo.numColorTargets, textures); GLenum *DrawBuffers = new GLenum[createInfo.numColorTargets]; for (uint32_t i = 0; i < createInfo.numColorTargets; i++) { glBindTexture(GL_TEXTURE_2D, textures[i]); GLint internalFormat; GLenum format; TranslateFormats(createInfo.colorFormats[i], format, internalFormat); // returns GL_RGBA and GL_RGBA glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, createInfo.width, createInfo.height, 0, format, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); DrawBuffers[i] = GL_COLOR_ATTACHMENT0 + i; glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, textures[i], 0); } if (createInfo.depthFormat != FORMAT_DEPTH_NONE) { GLenum depthFormat; switch (createInfo.depthFormat) { case FORMAT_DEPTH_16: depthFormat = GL_DEPTH_COMPONENT16; break; case FORMAT_DEPTH_24: depthFormat = GL_DEPTH_COMPONENT24; break; case FORMAT_DEPTH_32: depthFormat = GL_DEPTH_COMPONENT32; break; case FORMAT_DEPTH_24_STENCIL_8: depthFormat = GL_DEPTH24_STENCIL8; break; case FORMAT_DEPTH_32_STENCIL_8: depthFormat = GL_DEPTH32F_STENCIL8; break; } glGenTextures(1, &depthrenderbuffer); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); glTexImage2D(GL_TEXTURE_2D, 0, depthFormat, createInfo.width, createInfo.height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depthrenderbuffer, 0); } if (createInfo.numColorTargets > 0) glDrawBuffers(createInfo.numColorTargets, DrawBuffers); else glDrawBuffer(GL_NONE); if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) std::cout << "Framebuffer Incomplete\n"; glBindFramebuffer(GL_FRAMEBUFFER, 0); width = createInfo.width; height = createInfo.height; } // ... // FBO Creation FramebufferCreateInfo gbufferCI; gbufferCI.colorFormats = gbufferCFs.data(); gbufferCI.depthFormat = FORMAT_DEPTH_32; gbufferCI.numColorTargets = gbufferCFs.size(); gbufferCI.width = engine.settings.resolutionX; gbufferCI.height = engine.settings.resolutionY; gbufferCI.renderPass = nullptr; gbuffer = graphicsWrapper->CreateFramebuffer(gbufferCI); // Bind glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo); // Draw here... // Bind to textures glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textures[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textures[1]); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, textures[2]); glActiveTexture(GL_TEXTURE3); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); Here is an extract of my code. I can't think of anything else to include. I've really been butting my head into a wall trying to think of a reason but I can think of none and all my research yields nothing. Thanks in advance!

• Hi everyone, I've shared my 2D Game Engine source code. It's the result of 4 years working on it (and I still continue improving features ) and I want to share with the community. You can see some videos on youtube and some demo gifs on my twitter account.
This Engine has been developed as End-of-Degree Project and it is coded in Javascript, WebGL and GLSL. The engine is written from scratch.
This is not a professional engine but it's for learning purposes, so anyone can review the code an learn basis about graphics, physics or game engine architecture. Source code on this GitHub repository.
I'm available for a good conversation about Game Engine / Graphics Programming

• 16
• 14
• 16
• 10
• 18