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    • By codelyoko373
      I wasn't sure if this would be the right place for a topic like this so sorry if it isn't.
      I'm currently working on a project for Uni using FreeGLUT to make a simple solar system simulation. I've got to the point where I've implemented all the planets and have used a Scene Graph to link them all together. The issue I'm having with now though is basically the planets and moons orbit correctly at their own orbit speeds.
      I'm not really experienced with using matrices for stuff like this so It's likely why I can't figure out how exactly to get it working. This is where I'm applying the transformation matrices, as well as pushing and popping them. This is within the Render function that every planet including the sun and moons will have and run.
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    • By Jens Eckervogt
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    • By Jens Eckervogt
      Hello everyone
      For @80bserver8 nice job - I have found Google search. How did you port from Javascript WebGL to C# OpenTK.?
      I have been searched Google but it shows f***ing Unity 3D. I really want know how do I understand I want start with OpenTK But I want know where is porting of Javascript and C#?
       
      Thanks!
    • By mike44
      Hi
      I draw in a OpenGL framebuffer. All is fine but it eats FPS (frames per second), hence I wonder if I could execute the framebuffer drawing only every 5-10th loop or so?
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    • By cebugdev
      hi all,
      how to implement this type of effect ? 
      Also what is this effect called? this is considered volumetric lighting?
      what are the options of doing this? 
      a. billboard? but i want this to have the 3D effect that when we rotate the camera we can still have that 3d feel.
      b. a transparent 3d mesh? and we can animate it as well?
      need your expert advise.
       
      additional:
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      thanks!
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OpenGL How to fix camera view to a object in OpenGL?

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Plz forgive me about my poor english.

I'm new to OpenGL dev and this forums.  I followed the OpenGL tutorial from learnopengl, after finished the camera and model loading part, I wonder if I can do more about camera. 

I try to code a camera behavior that fix the view to a model, be more clear, like some games that you can fix the view to the enemy object, and while you walk around the view of camera still stick to the enemy object.  ( plz forgive my poor english )

I don't know the proper way to do that. My first thought is that If I need to bind camera view to an object, I need to know the location in the world coordinate of that object, then I can move the camera to see it.

I tried using raycasting picking to pick the object I loaded, but it is just that, I don't know what to do next. 

Could you guys tell me the way to do so? Some links of similar staff are great as well. Thanks.

Edited by AlexNaabal

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You will need a view matrix created with a LookAt function to indicate the position and the angle of the camera. You can use a math API that provides that or roll your own. There are some good APIs that I know of that provide that:

  • GLM (C++)
  • MonoGame (C#): see files Vector2.cs, Vector3.cs, Vector4.cs, Quaternion.cs and Matrix.cs
  • LinMath (C)
  • If you make your own math API, use the MonoGame or LinMath as example. It's more of a copy-paste task.

The LookAt matrix is usually made using a function like this:

	Matrix CreateLookAtMatrix(Vector3 camera_pos, Vector3 target, Vector3 up)
	

Then you can send the matrix (which is a 4x4 matrix) to your shader in the form of a float array (4x4 matrix has 16 elements).

In your shader, you multiply the view matrix (that we made with the LookAt function) with your vertex.

Edited by ferreiradaselva

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Thanks ferreiradaselvaI had already implemented some basic camera function. I'm sorry I forgot to mention that I'm using C++, GLFW and OpenGL. I can move around in FPS style camera, or use mouse dragging the camera. My question is how to " have the camera keep tracking the object ", or maybe " Let my eye( the camera ) looking at the object while walking around " more clearly.

Still appreciate your reply.

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I'm pretty sure you could do something like this

//In your update loop
float cameraDistance = 50.0f; //Some value that is within your nearZ / farZ
vec3 cameraPosition(playerPosition.x, playerPosition.y, playerPosition.z + cameraDistance);
camera.LookAt(cameraPosition, playerPosition, cameraUp);

Then as long as your camera gets passed to your shader you should be ok

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You will still need a view matrix. It can be generated with LookAt() or one of the other rotation matrices:

If you want a 3rd person camera, use the LookAt() and set the 3D vector target with the same value of the player position. And the camera_pos with a value that is the player position minus an offset value to keep the camera distant.

If you want a 1st person camera, you set the 3D vector camera_pos with the same value of the player position, however, the target is a bit more complicated, you can create a matrix that is the multiplication of two rotation matrices (rotation at axis Z and at axis X):

  • axis Z is the direction of the player
  • axis X is the axis that will determine if the player is looking up or down.

Then you send that multiplied matrix to your shader.

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1 hour ago, noodleBowl said:

I'm pretty sure you could do something like this


//In your update loop
float cameraDistance = 50.0f; //Some value that is within your nearZ / farZ
vec3 cameraPosition(playerPosition.x, playerPosition.y, playerPosition.z + cameraDistance);
camera.LookAt(cameraPosition, playerPosition, cameraUp);

Then as long as your camera gets passed to your shader you should be ok

1 hour ago, ferreiradaselva said:

You will still need a view matrix. It can be generated with LookAt() or one of the other rotation matrices:

If you want a 3rd person camera, use the LookAt() and set the 3D vector target with the same value of the player position. And the camera_pos with a value that is the player position minus an offset value to keep the camera distant.

If you want a 1st person camera, you set the 3D vector camera_pos with the same value of the player position, however, the target is a bit more complicated, you can create a matrix that is the multiplication of two rotation matrices (rotation at axis Z and at axis X):

  • axis Z is the direction of the player
  • axis X is the axis that will determine if the player is looking up or down.

Then you send that multiplied matrix to your shader.

Thanks noodleBowl and ferreiradaselva.  So the basic idea is update a lookAt( changing_cameraPos, fixed_objectPos, UpVector) for each frame? I wrote a demo to test it and it works, by setting the fixed_objectPos as (0,0,0), and use keyboard input to update cameraPos. 

And I find a word that might describe my question more clearly. It is the strafing. I try to code a circle strafing-ish movement.

So my final problem is about " get the 'fixed_objectPos' for lookAt function". I tried color picking and raycasting picking, but still confusing. Where I can read more about " the way to retrieve object position "? I've googled, and many answer leads me to picking. 

 

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