I’m doing the learnopengl tutorials and I’m trying one of the exercises in the Basic Lighting tutorial:
Try to move the light source around the scene over time using either sin or cos.
Although in my case, I’m using SDL which means I can’t use the following equations to rotate my light source around:
lightPos.x = 1.0f + sin(glfwGetTime()) * 2.0f;
lightPos.y = sin(glfwGetTime() / 2.0f) * 1.0f;
Right now, when I rotate my object, my light source rotates with it, however I want my light source to rotate separately from my object. This is what I have in my render loop which handles the rotation of the light and the object:
void OpenGLWindow::render()
{
lightPos.x = 1.0f + sin(SDL_GetTicks()/1000.0f) * 2.0f;
lightPos.y = sin((SDL_GetTicks()/1000.0f) / 2.0f) * 1.0f;
glm::mat4 model(1.0f);
//model = glm::translate(model, lightPos);
model = glm::rotate(model, lightPos.z, glm::vec3(0.0f, 0.0f, 1.0f));
//model = glm::rotate(model, lightPos.y, glm::vec3(0.0f, 1.0f, 0.0f));
model = glm::rotate(model, lightPos.x, glm::vec3(1.0f, 0.0f, 0.0f));
int modelMatLocation = glGetUniformLocation(shader, "lightMatrix");
glUniformMatrix4fv(modelMatLocation, 1, false, &model[0][0]);
// NOTE: glm::translate/rotate/scale apply the transformation by right-multiplying by the
// corresponding transformation matrix (T). IE glm::translate(M, v) = M * T, not T*M
// This means that the transformation you apply last, will effectively occur first
glm::mat4 modelMat(1.0f);
modelMat = glm::translate(modelMat, parentEntity.position);
modelMat = glm::rotate(modelMat, parentEntity.rotation.z, glm::vec3(0.0f, 0.0f, 1.0f));
modelMat = glm::rotate(modelMat, parentEntity.rotation.y, glm::vec3(0.0f, 1.0f, 0.0f));
modelMat = glm::rotate(modelMat, parentEntity.rotation.x, glm::vec3(1.0f, 0.0f, 0.0f));
modelMat = glm::scale(modelMat, parentEntity.scale);
int modelMatrixLoc = glGetUniformLocation(shader, "modelMatrix");
glUniformMatrix4fv(modelMatrixLoc, 1, false, &modelMat[0][0]);
}
And this is what I have in my vertex shader:
in vec3 position;
out vec3 FragPos;
out vec3 Normal;
uniform mat4 projectionMatrix;
uniform mat4 viewingMatrix;
uniform mat4 modelMatrix;
uniform mat4 lightMatrix;
void main()
{
vec4 transformedPosition = projectionMatrix * viewingMatrix * modelMatrix * lightMatrix * vec4(position, 1.0f);
gl_Position = transformedPosition;
FragPos = vec3(modelMatrix * vec4(position, 1.0));
Normal = mat3(transpose(inverse(modelMatrix))) * position;
}
Fragment shader:
out vec4 outColor;
in vec3 Normal;
in vec3 FragPos;
uniform vec3 lightPos;
uniform vec3 objectColor;
uniform vec3 lightColor;
uniform vec3 viewPos;
void main()
{
float ambientStrength = 0.06;
vec3 ambient = ambientStrength * lightColor;
vec3 norm = normalize(Normal);
vec3 lightDir = normalize(lightPos - FragPos);
float diff = max(dot(norm, lightDir), 0.0);
vec3 diffuse = diff * lightColor;
float specularStrength = 0.6;
vec3 viewDir = normalize(viewPos - FragPos);
vec3 reflectDir = reflect(-lightDir, norm);
float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
vec3 specular = specularStrength * spec * lightColor;
vec3 result = (ambient + diffuse + specular) * objectColor;
outColor = vec4(result, 1.0);
}
How do I rotate the light source only, without the object rotating also? I also posted the question on stackoverflow: