Sign in to follow this  

Still specular

This topic is 2490 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

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:
[b]VERTEX:[/b]


[code]#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);
}[/code]

[b]FRAGMENT:[/b][b]
[/b]

[code]#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);
}[/code]


What did i forget here?

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites
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 - [url="http://www.opengl.org/wiki/Mathematics_of_glTexGen"]http://www.opengl.or...ics_of_glTexGen[/url]

Havin' a good day, so also explanation:
[code]<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>[/code]

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:
[code]<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>[/code]
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...

Share this post


Link to post
Share on other sites
[quote name='karwosts' timestamp='1300997890' post='4790109']
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.
[/quote]
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.

[quote name='Vilem Otte' timestamp='1301005976' post='4790155']
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...
[/quote]
That's OK! This still might be helpfull some time after. When i will finish my "CryEngine" killer and rule this world!

[quote name='Hodgman' timestamp='1301009255' post='4790174']
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.
[/quote]
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:
[media]http://www.youtube.com/watch?v=jz3aDUJFOdc[/media]
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).

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites
Sign in to follow this