Fix OpenGL 2.1 specular lighting

src/graphics/opengl/gl21device.cpp

@@ -388,6 +388,7 @@ bool CGL21Device::Create()
         uni.modelMatrix = glGetUniformLocation(m_normalProgram, "uni_ModelMatrix");
         uni.normalMatrix = glGetUniformLocation(m_normalProgram, "uni_NormalMatrix");
         uni.shadowMatrix = glGetUniformLocation(m_normalProgram, "uni_ShadowMatrix");
+        uni.cameraPosition = glGetUniformLocation(m_normalProgram, "uni_CameraPosition");
 
         uni.primaryTexture = glGetUniformLocation(m_normalProgram, "uni_PrimaryTexture");
         uni.secondaryTexture = glGetUniformLocation(m_normalProgram, "uni_SecondaryTexture");
@@ -441,6 +442,7 @@ bool CGL21Device::Create()
         glUniformMatrix4fv(uni.modelMatrix, 1, GL_FALSE, matrix.Array());
         glUniformMatrix4fv(uni.normalMatrix, 1, GL_FALSE, matrix.Array());
         glUniformMatrix4fv(uni.shadowMatrix, 1, GL_FALSE, matrix.Array());
+        glUniform3f(uni.cameraPosition, 0.0f, 0.0f, 0.0f);
 
         glUniform1i(uni.primaryTexture, 0);
         glUniform1i(uni.secondaryTexture, 1);
@@ -653,6 +655,7 @@ void CGL21Device::SetTransform(TransformType type, const Math::Matrix &matrix)
     else if (type == TRANSFORM_VIEW)
     {
         Math::Matrix scale;
+        Math::Vector cameraPosition;
         scale.Set(3, 3, -1.0f);
         m_viewMat = Math::MultiplyMatrices(scale, matrix);
 
@@ -660,6 +663,12 @@ void CGL21Device::SetTransform(TransformType type, const Math::Matrix &matrix)
         m_combinedMatrix = Math::MultiplyMatrices(m_projectionMat, m_modelviewMat);
 
         glUniformMatrix4fv(m_uniforms[m_mode].viewMatrix, 1, GL_FALSE, m_viewMat.Array());
+
+        if (m_uniforms[m_mode].cameraPosition >= 0) {
+            cameraPosition.LoadZero();
+            cameraPosition = MatrixVectorMultiply(m_viewMat.Inverse(), cameraPosition);
+            glUniform3fv(m_uniforms[m_mode].cameraPosition, 1, cameraPosition.Array());
+        }
     }
     else if (type == TRANSFORM_PROJECTION)
     {

src/graphics/opengl/glutil.h

@@ -167,6 +167,8 @@ struct UniformLocations
     GLint shadowMatrix = -1;
     //! Normal matrix
     GLint normalMatrix = -1;
+    //! Camera position
+    GLint cameraPosition = -1;
 
     //! Primary texture sampler
     GLint primaryTexture = -1;

src/graphics/opengl/shaders/gl21/fs_normal.glsl

@@ -56,6 +56,7 @@ uniform Material uni_Material;
 uniform int uni_LightCount;
 uniform LightParams uni_Light[4];
 
+varying vec3 pass_CameraDirection;
 varying float pass_Distance;
 varying vec4 pass_Color;
 varying vec3 pass_Normal;
@@ -76,16 +77,17 @@ void main()
         vec4 specular = vec4(0.0f);
 
         vec3 normal = normalize(pass_Normal);
+        vec3 camera = normalize(pass_CameraDirection);
 
         for (int i = 0; i < uni_LightCount; i++)
         {
             LightParams light = uni_Light[i];
 
-            vec3 lightDirection = light.Position.xyz;
+            vec3 lightDirection = normalize(light.Position.xyz);
-            vec3 reflectDirection = -reflect(lightDirection, normal);
+            vec3 reflectAxis = normalize(lightDirection + camera);
 
             float diffuseComponent = clamp(dot(normal, lightDirection), 0.0f, 1.0f);
-            float specularComponent = clamp(pow(dot(normal, lightDirection + reflectDirection), 10.0f), 0.0f, 1.0f);
+            float specularComponent = pow(clamp(dot(normal, reflectAxis), 0.0f, 1.0f), 10.0f);
 
             ambient += light.Ambient;
             diffuse += diffuseComponent * light.Diffuse;

src/graphics/opengl/shaders/gl21/vs_normal.glsl

@@ -24,7 +24,9 @@ uniform mat4 uni_ViewMatrix;
 uniform mat4 uni_ModelMatrix;
 uniform mat4 uni_ShadowMatrix;
 uniform mat4 uni_NormalMatrix;
+uniform vec3 uni_CameraPosition;
 
+varying vec3 pass_CameraDirection;
 varying float pass_Distance;
 varying vec4 pass_Color;
 varying vec3 pass_Normal;
@@ -40,6 +42,7 @@ void main()
 
     gl_Position = uni_ProjectionMatrix * eyeSpace;
 
+    pass_CameraDirection = uni_CameraPosition - position.xyz;
     pass_Color = gl_Color;
     pass_Normal = normalize((uni_NormalMatrix * vec4(gl_Normal, 0.0f)).xyz);
     pass_Distance = abs(eyeSpace.z / eyeSpace.w);