# OpenGL GLSL 1.20 Lighting Problem

This topic is 1707 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

So, I've been following the tuts from [url="http://www.opengl-tutorial.org/"]http://www.opengl-tutorial.org[/url], (using the opengl 2.1 versions) and came across a problem in Tutorial 8: Basic Shading. Basically, my shading comes out calculated wrong(noticable around the edges of the triangle faces).

After hours of comparing the tut code with my code, i could find anythign wrong. I finally jus copied and pasted everything from the tut, but nothing help. I am pretty sure the problem with the shaders, here is the code:

#version 120

// Interpolated values from the vertex shaders
varying vec2 UV;
varying vec3 Position_worldspace;
varying vec3 Normal_cameraspace;
varying vec3 EyeDirection_cameraspace;
varying vec3 LightDirection_cameraspace;

// Values that stay constant for the whole mesh.
uniform sampler2D myTextureSampler;
uniform mat4 MV;
uniform vec3 LightPosition_worldspace;

void main(){

// Light emission properties
// You probably want to put them as uniforms
vec3 LightColor = vec3(1,1,1);
float LightPower = 30.0;

// Material properties
vec3 MaterialDiffuseColor = texture2D(myTextureSampler,UV).rgb;
vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor;
vec3 MaterialSpecularColor = vec3(0.3,0.3,0.3);

// Distance to the light
float distance2 = length( LightPosition_worldspace - Position_worldspace );

// Normal of the computed fragment, in camera space
vec3 n = normalize( Normal_cameraspace );
// Direction of the light (from the fragment to the light)
vec3 l = normalize( LightDirection_cameraspace );
// Cosine of the angle between the normal and the light direction,
// clamped above 0
//  - light is at the vertical of the triangle -> 1
//  - light is perpendicular to the triangle -> 0
//  - light is behind the triangle -> 0
float cosTheta = clamp( dot( n,l ), 0.0,1.0);

// Eye vector (towards the camera)
vec3 E = normalize(EyeDirection_cameraspace);
// Direction in which the triangle reflects the light
vec3 R = reflect(-l,n);
// Cosine of the angle between the Eye vector and the Reflect vector,
// clamped to 0
//  - Looking into the reflection -> 1
//  - Looking elsewhere -> < 1
float cosAlpha = clamp( dot( E,R ), 0,1 );

gl_FragColor.rgb =

// Diffuse : "color" of the object
MaterialDiffuseColor* LightColor * LightPower /(distance2*distance2) ;

}

#version 120

// Input vertex data, different for all executions of this shader.
attribute vec3 vertexPosition_modelspace;
attribute vec2 vertexUV;
attribute vec3 vertexNormal_modelspace;

// Output data ; will be interpolated for each fragment.
varying vec2 UV;
varying vec3 Position_worldspace;
varying vec3 Normal_cameraspace;
varying vec3 EyeDirection_cameraspace;
varying vec3 LightDirection_cameraspace;

// Values that stay constant for the whole mesh.
uniform mat4 MVP;
uniform mat4 V;
uniform mat4 M;
uniform vec3 LightPosition_worldspace;
uniform int vertex_image_type;

void main(){

// Output position of the vertex, in clip space : MVP * position
gl_Position =  MVP * vec4(vertexPosition_modelspace,1);

// Position of the vertex, in worldspace : M * position
Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz;

// Vector that goes from the vertex to the camera, in camera space.
// In camera space, the camera is at the origin (0,0,0).
vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz;
EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace;

// Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity.
vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz;
LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace;

// Normal of the the vertex, in camera space
Normal_cameraspace = ( V * M * vec4(vertexNormal_modelspace,0)).xyz; // Only correct if ModelMatrix does not scale the model ! Use its inverse transpose if not.

// UV of the vertex. No special space for this one.
UV = vertexUV;
if (vertex_image_type==2)
{
UV.y =-UV.y;//invierse v if dds
}
}


i just kept the diffuse, thats where the problem seems to be. maybe the problem is with the glsl and opengl versions? edit: Just to add some more info. I kinda think the problem has something to do with that cosTheta variable. when I remove it from the equation, the problem is no longer there(but faces are lit up eventhough they are facing away from the light) I understand the purpose of the cosTheta is to calculate the brightness based on the angle of the face compared to the angle of the light, but maybe there is something wrong here...

Edited by handoman

##### Share on other sites

okay so I just downloaded the source files from http://www.opengl-tutorial.org and built the projects. I ran the tut 8 project and it seems to be working perfect. So, i guess i will be studying the code to see where i went wrong.

• ### Similar Content

• By xhcao
Does sync be needed to read texture content after access texture image in compute shader?
My simple code is as below,
glUseProgram(program.get());
glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
glDispatchCompute(1, 1, 1);
// Does sync be needed here?
glUseProgram(0);
GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture[1], 0);
glReadPixels(0, 0, kWidth, kHeight, GL_RED_INTEGER, GL_UNSIGNED_INT, outputValues);

Compute shader is very simple, imageLoad content from texture[0], and imageStore content to texture[1]. Does need to sync after dispatchCompute?

• My question: is it possible to transform multiple angular velocities so that they can be reinserted as one? My research is below:

• I have this code below in both my vertex and fragment shader, however when I request glGetUniformLocation("Lights[0].diffuse") or "Lights[0].attenuation", it returns -1. It will only give me a valid uniform location if I actually use the diffuse/attenuation variables in the VERTEX shader. Because I use position in the vertex shader, it always returns a valid uniform location. I've read that I can share uniforms across both vertex and fragment, but I'm confused what this is even compiling to if this is the case.

#define NUM_LIGHTS 2
struct Light
{
vec3 position;
vec3 diffuse;
float attenuation;
};
uniform Light Lights[NUM_LIGHTS];

• By pr033r
Hello,
I have a Bachelor project on topic "Implenet 3D Boid's algorithm in OpenGL". All OpenGL issues works fine for me, all rendering etc. But when I started implement the boid's algorithm it was getting worse and worse. I read article (http://natureofcode.com/book/chapter-6-autonomous-agents/) inspirate from another code (here: https://github.com/jyanar/Boids/tree/master/src) but it still doesn't work like in tutorials and videos. For example the main problem: when I apply Cohesion (one of three main laws of boids) it makes some "cycling knot". Second, when some flock touch to another it scary change the coordination or respawn in origin (x: 0, y:0. z:0). Just some streng things.
I followed many tutorials, change a try everything but it isn't so smooth, without lags like in another videos. I really need your help.
My code (optimalizing branch): https://github.com/pr033r/BachelorProject/tree/Optimalizing
Exe file (if you want to look) and models folder (for those who will download the sources):
http://leteckaposta.cz/367190436
Thanks for any help...

• By Andrija
I am currently trying to implement shadow mapping into my project , but although i can render my depth map to the screen and it looks okay , when i sample it with shadowCoords there is no shadow.
Here is my light space matrix calculation
mat4x4 lightViewMatrix; vec3 sun_pos = {SUN_OFFSET * the_sun->direction[0], SUN_OFFSET * the_sun->direction[1], SUN_OFFSET * the_sun->direction[2]}; mat4x4_look_at(lightViewMatrix,sun_pos,player->pos,up); mat4x4_mul(lightSpaceMatrix,lightProjMatrix,lightViewMatrix); I will tweak the values for the size and frustum of the shadow map, but for now i just want to draw shadows around the player position
the_sun->direction is a normalized vector so i multiply it by a constant to get the position.
player->pos is the camera position in world space
the light projection matrix is calculated like this:
uniform mat4 light_space_matrix; void main() { gl_Position = light_space_matrix * transfMatrix * vec4(position, 1.0f); } Shadow fragment shader:
out float fragDepth; void main() { fragDepth = gl_FragCoord.z; } I am using deferred rendering so i have all my world positions in the g_positions buffer