# OpenGL Rendering a heightmap

## Recommended Posts

Hey all. I have created a heightmap class, storing the x, y, and z coordinates of each point in the rectangular heightmap. Basically, the question is this: How should I go about rendering the heightmap in a fairly efficient manner? I know that OpenGL (and 3d rendering in general) is optimized for displaying huge quantities of triangles within a single call to glBegin()/glEnd(). Don't worry about textures or anything; I just want to get the heightmap on the screen for now. I tried this algorithm that I came up with in the car, but it (obviously, looking back on it now) just displays a 2d triangle when the height map is raised from the rest, instead of a kind of "pyramid", which is what I want:
bool up_or_down = false;
for (float y = 0; y < map_height; ++i)
{
glBegin(GL_TRIANGLE_STRIP);
for (float x = 0; x < map_width; ++x)
{
do
{
glVertex3f( x, y + (float)up_or_down, HeightAtLocation(x, y + up_or_down);
up_or_down = !up_or_down;
} while (up_or_down);
}
glEnd();
}

If you are willing, and you don't understand how the algorithm works, then draw it out on paper, and you will see what it does. Unfortunately, it doesn't work. I was just wondering if anyone could point me to some examples of how this might be done. Thanks.

##### Share on other sites
ismakefire    122
I must admit, that's the weirds way I've seen someone try to draw a surface. That's not a bad thing, you've got imagination, but have a do while handle two cases and converting a bool to float... hehe.

Anyway, if you want efficent you'd be generating to field before hand and send it off to OpenGL via arrays or something else the next 50 posters post about shortly.

Firstly, so that other know what your doing and so your computersaves a jump(at the cost some very expendable program size.) Do this PLZ!
glVertex3f( x, y, HeightAtLocation(x, y);
glVertex3f( x, y+1, HeightAtLocation(x, y+1);

2nd, "or (float y = 0; y < map_height; ++i)"???, I'm looking at the ++i

You've got the right idea, and you should be drawing a plane or whatever if that function is being nice... but you might want to post that as well.

:) IsMAkeFire

##### Share on other sites
OK, yeah, it was weird. Must have been fumes. Anyways, I turned on wireframe mode and discovered that actually, it was *mostly* rendering it as a "pyramid", except for the bottom-left and top-right corners, which weren't being included as part of the pyramid. Let me get a screenshot... just a minute.

[EDIT] Here ya go. Notice, again, top-right and bottom-left corners of the raised portion:

[EDIT2] And here is the new algorithm:

void RenderHeightmap(const HeightMap * height_map){    glColor3f(0.0f, 1.0f, 0.0f);    for (float i = 0.0f; i < (float)height_map->Height(); ++i)    {        glBegin(GL_TRIANGLE_STRIP);        for ( float x = 0.0f; x < (float)height_map->Width(); ++x)        {                glVertex3f(x, i, height_map->GetTileInfo((int)x, (int)i).height);                glVertex3f(x, i + 1.0f, height_map->GetTileInfo((int)x, (int)(i + 1.0f)).height);        }        glEnd();    }}

##### Share on other sites
ismakefire    122
First: :)

Ok, what you've got here is the flaw in drawing quads with pairs of triangles. This only solutions are to double the number of triangles you use(4 per quad), create a special location that ignores the mesh and draw a seporate model(probly not what you want, but it's what myth did), or suck it up cuz that's life.

Now oyu can ether go through the plane like before but rather then drawing strips draw quads like so:

glBegin(GL_TRAINGLE_FAN);
glVertex3f(x+0.5f, y+0.5f, someZFunciton(x+0.5f, y+0.5f));
glVertex3f(x, y, someZFunciton(x, y));
glVertex3f(x+1, y, someZFunciton(x+1, y));
glVertex3f(x+1, y+1, someZFunciton(x+1, y+1));
glVertex3f(x, y+1, someZFunciton(x, y+1));
glEnd();

1---2
|. 0.|
4---3

##### Share on other sites
zedzeek    528
the best way is to subdevide the terrain up into patch say 17x17 or 33x33 vertices

##### Share on other sites
ismakefire    122
One last thing, if you want to be fast about drawing those kinds of quads you can draw them diaganally, but don't go out of your way unless you're going to store it in a list or as an OpenGL array.

IsMakeFire

##### Share on other sites
Quote:
 Original post by ismakefireFirst: :)Ok, what you've got here is the flaw in drawing quads with pairs of triangles. This only solutions are to double the number of triangles you use(4 per quad), create a special location that ignores the mesh and draw a seporate model(probly not what you want, but it's what myth did), or suck it up cuz that's life.Now oyu can ether go through the plane like before but rather then drawing strips draw quads like so:glBegin(GL_TRAINGLE_FAN);glVertex3f(x+0.5f, y+0.5f, someZFunciton(x+0.5f, y+0.5f));glVertex3f(x, y, someZFunciton(x, y));glVertex3f(x+1, y, someZFunciton(x+1, y));glVertex3f(x+1, y+1, someZFunciton(x+1, y+1));glVertex3f(x, y+1, someZFunciton(x, y+1));glEnd();My drawing of the quad:1---2|. 0.|4---3

Well, I'm not sure how you would access a point in between two points, but this would work if I could :)

Not sure what you're talking about, zedzeek.

Anyways, I think I'm going to try the idea of using four triangles to draw each quad. I'm not sure how you would do that, though, so I'm going to turn to you. How would you suggest modifying/adding on to the algorithm to accomplish this? And yes, I did try it myself to the best of my abilities, but I guess I'm just not that smart :)

##### Share on other sites
zedzeek    528
Quote:
 Not sure what you're talking about, zedzeek.

Quote:
 Hey all. I have created a heightmap class, storing the x, y, and z coordinates of each point in the rectangular heightmap. Basically, the question is this:How should I go about rendering the heightmap in a fairly efficient manner?

the first thing u should do instead of what has been mentioned is break the terrain up into square chunks, eg 33x33 verts. this way u can stick a boundingshape around each chunk + see if its in the modelview frustum, this is the first thing u should do before u worry about how to actually draw the thing eg VBOs using strips etc

## Create an account

Register a new account

• ### Similar Content

• 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
• By C0dR
I would like to introduce the first version of my physically based camera rendering library, written in C++, called PhysiCam.
Physicam is an open source OpenGL C++ library, which provides physically based camera rendering and parameters. It is based on OpenGL and designed to be used as either static library or dynamic library and can be integrated in existing applications.

The following features are implemented:
Physically based sensor and focal length calculation Autoexposure Manual exposure Lense distortion Bloom (influenced by ISO, Shutter Speed, Sensor type etc.) Bokeh (influenced by Aperture, Sensor type and focal length) Tonemapping
You can find the repository at https://github.com/0x2A/physicam

I would be happy about feedback, suggestions or contributions.

• 10
• 10
• 18
• 9
• 9