c++ - OpenGL: How to make light to be independent of rotation? -

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i have diffuse lighting shader seems work when object not rotating. however, when apply rotation transform, light seems rotate along object. it's object , light stay still camera 1 moves around object.

here's vertex shader code:

#version 110  uniform mat4 projectionmatrix; uniform mat4 modelviewmatrix; uniform vec3 lightsource;  attribute vec3 vertex; attribute vec3 normal;  varying vec2 texcoord;  void main() {     gl_position = projectionmatrix * modelviewmatrix * vec4( vertex, 1.0 );      vec3 n = gl_normalmatrix * normalize( normal );     vec4 v = modelviewmatrix * vec4( vertex, 1.0 );     vec3 l = normalize( lightsource - v.xyz );      float ndotl = max( 0.0, dot( n, l ) );      gl_frontcolor = vec4( gl_color.xyz * ndotl, 1.0 );      gl_texcoord[0] = gl_multitexcoord0; }

and here's code rotation:

scene.loadidentity(); scene.translate( 0.0f, -5.0f, -20.0f ); scene.rotate( angle, 0.0f, 1.0f, 0.0f ); object->draw();

i sent eye-space light position through gluniform3f, inside object->draw() function. light position static, , defined as:

glm::vec4 lightpos( light.x, light.y, light.z, 1.0 ); glm::vec4 lighteyepos = modelviewmatrix * lightpos; gluniform3f( uniforms.lightsource, lighteyepos.x, lighteyepos.y, lighteyepos.z );

what's wrong approach?

edit: glm::lookat code

scene scene; scene.loadmatrix( projection ); scene.setmatrixmode( scene::modelview ); scene.loadidentity(); scene.setviewmatrix( glm::lookat( glm::vec3( 0.0f, 0.0f, 0.0f ), glm::vec3( 0.0f, -5.0f, -20.0f ), glm::vec3( 0.0f, 1.0f, 0.0f ) ) );

the setviewmatrix code:

void scene::setviewmatrix( const glm::mat4 &matrix ) {     viewmatrix = matrix;     transformmatrix( matrix ); }

then changed modelviewmatrix used viewmatrix:

glm::vec4 lightpos( light.x, light.y, light.z, 1.0 ); glm::vec4 lighteyepos = viewmatrix * lightpos; gluniform3f( uniforms.lightsource, lighteyepos.x, lighteyepos.y, lighteyepos.z );

statement 1: light position static.

statement 2: lighteyepos = modelviewmatrix * lightpos;

these 2 claims inconsistent. if light position supposed static, shouldn't applying rotated model matrix it.

if lightpos defined in world coordinates, should multiply viewmatrix not modelviewmatrix. modelviewmatrix contains model matrix, contains model's rotation (you don't want apply fixed light source).


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