Sign in to follow this  
ComradeSlice

OpenGL OpenGL Camera

Recommended Posts

ComradeSlice    110

This is my first post (which is sad because I've been a member for years) Hello, world!

 

I've got to say, I'm eager to learn from what is probably a very obvious mistake I'm making. This is my code for a free-flying camera. I don't have any movement code yet, so the camera just rotates around the origin. As I move the camera, it's almost as if the axis is slowly drifting, until I'm no longer rotating on the right axes!

glm::float_t scale = -500.0;
m_LookLR += (glm::float_t)analogEvent.x / scale;
m_LookUD += (glm::float_t)analogEvent.y / scale;

m_LookUD = glm::clamp<glm::float_t>(m_LookUD, -glm::half_pi<glm::float_t>(), glm::half_pi<glm::float_t>());

const glm::quat rotLR(0, glm::sin(m_LookLR / 2.0), 0, glm::cos(m_LookLR / 2.0));
const glm::quat rotUD(0, 0, glm::sin(m_LookUD / 2.0), glm::cos(m_LookUD / 2.0));
oglContext->rotViewMatrix = glm::mat4_cast(rotLR * rotUD);

From here, "rotViewMatrix" is multiplied against the translation view matrix and the projection matrix. Model matrix is multiplied in the shader.

 

I've seen other posts where some people use Euler Angles and others use Quaternions. I'm completely open to suggestion. Ease of use doesn't really bother me, but if one is a couple of floats and the other takes 2K of memory I'd go with the smaller footprint.

 

Regards,

ComradeSlice

 

EDIT: editor won't let me add spacing before/after the code block. Sorry for scrunched up post...

Edited by ComradeSlice

Share this post


Link to post
Share on other sites
HappyCoder    5052

I'm not sure what you mean by the axis drifting, but there is something that looks off in your code.

looking at the quaternion reference form glm, it looks like you are getting the parameter order wrong in the quat constructor. It expects w first, you are passing it in last.

 

Also, usually the forward vector for the camera goes along the z axis. For your up down rotation, it looks like you are rotating around the z axis. This will result in the camera rolling instead of pitching. Try switching the rotUP to rotate around the x axis.

Share this post


Link to post
Share on other sites
ComradeSlice    110

I'm not sure what you mean by the axis drifting, but there is something that looks off in your code.

looking at the quaternion reference form glm, it looks like you are getting the parameter order wrong in the quat constructor. It expects w first, you are passing it in last.

 

Also, usually the forward vector for the camera goes along the z axis. For your up down rotation, it looks like you are rotating around the z axis. This will result in the camera rolling instead of pitching. Try switching the rotUP to rotate around the x axis.

 

Now that makes a lot more sense. I changed the camera code accordingly:

const glm::quat rotLR(glm::cos(m_LookLR / 2.0), 0, glm::sin(m_LookLR / 2.0), 0);
const glm::quat rotUD(glm::cos(m_LookUD / 2.0), glm::sin(m_LookUD / 2.0), 0, 0);

I was still having issues with the camera rolling after this, but then I remembered reading about order of operations in glm. I changed the order that both quaternions were being multiplied:

//oglContext->rotViewMatrix = glm::mat4_cast(rotLR*rotUD);
oglContext->rotViewMatrix = glm::mat4_cast(rotUD*rotLR);

Voilà! It works perfectly now. Thank you!

Share this post


Link to post
Share on other sites
ComradeSlice    110

I was a little surprised to see that you take issue with OpenGL because of legacy support and the API in general. I was reading what you wrote in a thread with someone asking for beginner's advice. Do you think OpenGL is too old to really take full advantage of the graphics resources today's hardware has to offer? I'm sticking with OGL for cross-platform support, but if there were significant potential performance gains from using DX11, I would make a Windows wrapper to support both.

Share this post


Link to post
Share on other sites
HappyCoder    5052

OpenGL is still a good option. I just recommended DirectX because of an experience I had learning OpenGL. I had been using OpenGL for a few years now. I then learned DirectX11 and by using DirectX I learned that the way I have been using OpenGL was outdated. A few examples of features are constant buffers, samplers, and seperate shader objects. DirectX forced me to use these features since it didn't allow me to do them the old way. OpenGL let me stay in the past, that is all I was saying there.

 

I don't think OpenGL is bad, what you learn using OpenGL will carry over to DirectX, you just need to learn a few API differences.

Share this post


Link to post
Share on other sites
Kaptein    2224

All you had to do was create a forward compatible context, HappyCoder.

Some pros and cons:

DX:

* object-oriented

* locked-in (windows, xbox, ...)

* has wonderful tools to help you find problems

* microsoft has reference tools that forces implementations to conform

 

GL:

* C API, with a zillion bindings (meaning you can use absolutely any language you so desire, eg. Python, Java)

* multi-platform

* has had really bad tools and support for a long long time, but that's probably changing now with vogl(?) and co.

* hasn't had reference implementations, but that may change (there's a reference shader compiler now at least)

* has a baggage train from dinosaur era (which you can disable with forward-compatibility)

 

With that said, I still prefer OpenGL. Modern OpenGL has no significant problems. I don't know which is better for beginners. I'm just going to assume DirectX, but that's only if beginners actually use debugging tools.....

Edited by Kaptein

Share this post


Link to post
Share on other sites
tmason    326

All you had to do was create a forward compatible context, HappyCoder.
Some pros and cons:
DX:
* object-oriented
* locked-in (windows, xbox, ...)
* has wonderful tools to help you find problems
* microsoft has reference tools that forces implementations to conform
 
GL:
* C API, with a zillion bindings (meaning you can use absolutely any language you so desire, eg. Python, Java)
* multi-platform
* has had really bad tools and support for a long long time, but that's probably changing now with vogl(?) and co.
* hasn't had reference implementations, but that may change (there's a reference shader compiler now at least)
* has a baggage train from dinosaur era (which you can disable with forward-compatibility)
 
With that said, I still prefer OpenGL. Modern OpenGL has no significant problems. I don't know which is better for beginners. I'm just going to assume DirectX, but that's only if beginners actually use debugging tools.....


I have starting doing OpenGL dev only about 6+ months ago and so far it has been OK. Compared to DirectX OpenGL seems easier.

I believe the biggest problem that I face as a new Dev with OpenGL is the huge change OpenGL had a few years ago with modernization (OpenGL 3+)

That left a huge gap between all of the information out there regarding "old" OpenGL and new; in many ways it looks like a whole new language compared to the old stuff.

Once you get the hang of it everything starts getting easier; it seems to me due to OpenGL being the true cross-platform low level graphics API that DirectX's days are numbered.

Share this post


Link to post
Share on other sites
ComradeSlice    110

I have starting doing OpenGL dev only about 6+ months ago and so far it has been OK. Compared to DirectX OpenGL seems easier.

I believe the biggest problem that I face as a new Dev with OpenGL is the huge change OpenGL had a few years ago with modernization (OpenGL 3+)

That left a huge gap between all of the information out there regarding "old" OpenGL and new; in many ways it looks like a whole new language compared to the old stuff.

Once you get the hang of it everything starts getting easier; it seems to me due to OpenGL being the true cross-platform low level graphics API that DirectX's days are numbered.

 

 

I think I'm almost at the point where I can say I've got the hang of it. It used to drive me crazy how most of the material out there is for legacy OpenGL. I was only able to pave my way in modern OpenGL after finding a very small number of wonderful modern tutorials. I completely agree that OpenGL 3+ looks like a completely different API, it being Object Oriented vs the ugly State Machine in earlier standards.

 

I appreciate all the opinions. I now feel justified in using OpenGL on Windows, and not just using it lazily to make a half-ass port. HappyCoder, thanks for help with the camera.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By povilaslt2
      Hello. I'm Programmer who is in search of 2D game project who preferably uses OpenGL and C++. You can see my projects in GitHub. Project genre doesn't matter (except MMO's :D).
    • By ZeldaFan555
      Hello, My name is Matt. I am a programmer. I mostly use Java, but can use C++ and various other languages. I'm looking for someone to partner up with for random projects, preferably using OpenGL, though I'd be open to just about anything. If you're interested you can contact me on Skype or on here, thank you!
      Skype: Mangodoor408
    • By tyhender
      Hello, my name is Mark. I'm hobby programmer. 
      So recently,I thought that it's good idea to find people to create a full 3D engine. I'm looking for people experienced in scripting 3D shaders and implementing physics into engine(game)(we are going to use the React physics engine). 
      And,ye,no money =D I'm just looking for hobbyists that will be proud of their work. If engine(or game) will have financial succes,well,then maybe =D
      Sorry for late replies.
      I mostly give more information when people PM me,but this post is REALLY short,even for me =D
      So here's few more points:
      Engine will use openGL and SDL for graphics. It will use React3D physics library for physics simulation. Engine(most probably,atleast for the first part) won't have graphical fron-end,it will be a framework . I think final engine should be enough to set up an FPS in a couple of minutes. A bit about my self:
      I've been programming for 7 years total. I learned very slowly it as "secondary interesting thing" for like 3 years, but then began to script more seriously.  My primary language is C++,which we are going to use for the engine. Yes,I did 3D graphics with physics simulation before. No, my portfolio isn't very impressive. I'm working on that No,I wasn't employed officially. If anybody need to know more PM me. 
       
    • 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?
    • By Kjell Andersson
      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.
  • Popular Now