Jump to content

  • Log In with Google      Sign In   
  • Create Account

We're offering banner ads on our site from just $5!

1. Details HERE. 2. GDNet+ Subscriptions HERE. 3. Ad upload HERE.


Still specular


Old topic!
Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.

  • You cannot reply to this topic
6 replies to this topic

#1 uhfath   Members   -  Reputation: 100

Like
0Likes
Like

Posted 24 March 2011 - 01:47 PM

Hi!

I'm trying to implement some specular reflections. All looks OK, but specular spot isn't moving when i turn the camera. Here are the shaders:
VERTEX:


#version 330 core

uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
uniform mat4 modelViewProjMatrix;

uniform vec3 lightDirection;
uniform vec3 cameraPosition;

layout(location = 0) in vec3 Position;
layout(location = 1) in vec3 Normal;

out vec3 ViewDirection;
out vec3 LightDirection;
out vec3 VertexNormal;

void main()
{
  gl_Position = modelViewProjMatrix * vec4(Position, 1.0f);

  vec3 worldNormal = mat3(modelMatrix) * Normal;
  vec4 worldPosition = modelMatrix * vec4(Position, 1.0f);

  LightDirection = -lightDirection;
  ViewDirection = (cameraPosition - worldPosition.xyz);
  VertexNormal = (worldNormal);
}

FRAGMENT:


#version 330 core

layout(location = 0, index = 0) out vec4 Color;

in vec3 ViewDirection;
in vec3 LightDirection;
in vec3 VertexNormal;

void main()
{
  vec3 normal = normalize(VertexNormal);
  vec3 lightDirection = normalize(LightDirection);
  vec3 viewDirection = normalize(ViewDirection);
  vec3 halfVector = normalize(lightDirection + viewDirection);

  float diffuseIntensity = max(dot(lightDirection, normal), 0.0f);
  float specularIntensity = pow(max(dot(halfVector, normal), 0.0f), 10.0f);

  Color = vec4(specularIntensity);
}


What did i forget here?

Sponsor:

#2 karwosts   Members   -  Reputation: 840

Like
0Likes
Like

Posted 24 March 2011 - 02:18 PM

Do you mean its not changing when you move the camera, or turn the camera?

Its not clear from your code why you think turning the camera should change the output.
My Projects:
Portfolio Map for Android - Free Visual Portfolio Tracker
Electron Flux for Android - Free Puzzle/Logic Game

#3 Vilem Otte   Crossbones+   -  Reputation: 1469

Like
-1Likes
Like

Posted 24 March 2011 - 04:32 PM

In this case, some trickery with matrices is needed - on ancient Fixed function we generated projection coordinates with glTexGen and parameter GL_REFLECTION_MAP. How to compute the exact coordinates is described here - http://www.opengl.or...ics_of_glTexGen

Havin' a good day, so also explanation:
<BR>for(i=0; i<total; i++)<BR>{<BR>   myEyeVertex = MatrixTimesVector(ModelviewMatrix, myVertex[i]);<BR>   myEyeVertex = Normalize(myEyeVertex);<BR>   myEyeNormal = VectorTimesMatrix(myNormal[i], InverseModelviewMatrix);<BR>   dotResult = 2.0 * dot3D(myEyeNormal, myEyeNormal);<BR>   //I am emphasizing that we write to s and t and r. Used to sample a cubemap.<BR>   myTexCoord[i].s = myEyeVertex.x - myEyeNormal.x * dotResult;<BR>   myTexCoord[i].t = myEyeVertex.y - myEyeNormal.y * dotResult;<BR>   myTexCoord[i].r = myEyeVertex.z - myEyeNormal.z * dotResult;<BR>}<BR>

First compute vector from eye to vertex (as described here - gl_ModelViewMatrix * gl_Vertex) and normalize it.
Then compute eye normal that would be gl_NormalMatrix * gl_Normal and compute 2 times dot product of eye normal vector and eye normal vector, in the end generate all three coordinates as described in code, in GLSL it might look as:
<BR>vec4 eye_vert = normalize(gl_ModelViewMatrix * gl_Vertex);<BR>vec3 eye_norm = gl_NormalMatrix * gl_Normal;<BR>float dp = 2.0 * dot(eye_norm, eye_norm)<BR>reflection_coord.x = eye_vert.x - eye_norm.x * dp;<BR>reflection_coord.y = eye_vert.y - eye_norm.y * dp;<BR>reflection_coord.z = eye_vert.z - eye_norm.z * dp;<BR><BR>

Note that reflection_coord is vec3 going out to geometry and/or fragment shader (pixel shader), I also don't remember if you didn't have to do eye_vert.xyz = eye_vert.xyz / eye_vert.w; although it should be (according to OpenGL.org wiki correct, and also I didn't have time to test it with built-in matrices, as I build my own matrices that I pass to glsl and I'm not using built-in ones).

EDIT: Sorry, my mistake - I was thinking it is cubemap reflection (my appologize, I actually posted in wrong forum and realized just today ... could mod please delete this post (when reading this)? It's definitely not related, Thank you ... ) I wonder if I can report myself? And also note that there isn't working function of delete your own post on forum...

My current blog on programming, linux and stuff - http://gameprogrammerdiary.blogspot.com


#4 Hodgman   Moderators   -  Reputation: 31177

Like
0Likes
Like

Posted 24 March 2011 - 05:27 PM

As karwosts said, and as your code shows, specular is based in the position of the camera, position of the fragment and the normal. When you turn the camera, it should not change.

#5 uhfath   Members   -  Reputation: 100

Like
0Likes
Like

Posted 25 March 2011 - 09:27 AM

Do you mean its not changing when you move the camera, or turn the camera?

Its not clear from your code why you think turning the camera should change the output.

Yeah. Sorry. I meant when the camera is exactly turned. I thought that it should change because of that. I saw that in many games.

EDIT: Sorry, my mistake - I was thinking it is cubemap reflection (my appologize, I actually posted in wrong forum and realized just today ... could mod please delete this post (when reading this)? It's definitely not related, Thank you ... ) I wonder if I can report myself? And also note that there isn't working function of delete your own post on forum...

That's OK! This still might be helpfull some time after. When i will finish my "CryEngine" killer and rule this world!

As karwosts said, and as your code shows, specular is based in the position of the camera, position of the fragment and the normal. When you turn the camera, it should not change.

Perhaps there is some missunderstanding caused by me. Sorry about that.
Right now i'm testing my scene with a "chase" type camera. That means it's turned around the object.
This is the video that shows what i'm talking about:
http://www.youtube.com/watch?v=jz3aDUJFOdc
It was made in one of the engines i used. Light source is directional and stationary.
What i want to achive is something similar with the same conditions - turning the camera around the object - specular should move. Right now it's stays still regardless of camera position around it (can't make another video right at this moment).

#6 davidleonardcook   Members   -  Reputation: 102

Like
0Likes
Like

Posted 25 March 2011 - 01:04 PM

As you move the camera, check that the value you set for LightDirection remains constant, and that the value you set for CameraPosition changes. You might accidentally be computing these in camera space, instead of world space.

#7 uhfath   Members   -  Reputation: 100

Like
0Likes
Like

Posted 26 March 2011 - 01:22 AM

I've checked them with gDebugger and it seems that lightDirection is constant and cameraPosition changes.
Perhaps there is something wrong with the CPU part of code. I just wanted to verify that my shaders are correct. If that's so, then i will be looking at the other end.




Old topic!
Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.



PARTNERS