How to get keyboard navigation in OpenGL - c++

Question

I'm trying to create a solar system in OpenGL. I have the basic code for earth spinning on its axis and im trying to set the camera to move with the arrow keys.
using namespace std;
using namespace glm;
const int windowWidth = 1024;
const int windowHeight = 768;
GLuint VBO;
int NUMVERTS = 0;
bool* keyStates = new bool[256]; //Create an array of boolean values of length 256 (0-255)
float fraction = 0.1f; //Fraction for navigation speed using keys
// Transform uniforms location
GLuint gModelToWorldTransformLoc;
GLuint gWorldToViewToProjectionTransformLoc;
// Lighting uniforms location
GLuint gAmbientLightIntensityLoc;
GLuint gDirectionalLightIntensityLoc;
GLuint gDirectionalLightDirectionLoc;
// Materials uniform location
GLuint gKaLoc;
GLuint gKdLoc;
// TextureSampler uniform location
GLuint gTextureSamplerLoc;
// Texture ID
GLuint gTextureObject[11];
//Navigation variables
float posX;
float posY;
float posZ;
float viewX = 0.0f;
float viewY = 0.0f;
float viewZ = 0.0f;
float dirX;
float dirY;
float dirZ;
vec3 cameraPos = vec3(0.0f,0.0f,5.0f);
vec3 cameraView = vec3(viewX,viewY,viewZ);
vec3 cameraDir = vec3(0.0f,1.0f,0.0f);
These are all my variables that im using to edit the camera.
static void renderSceneCallBack()
{
// Clear the back buffer and the z-buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Create our world space to view space transformation matrix
mat4 worldToViewTransform = lookAt(
cameraPos, // The position of your camera, in world space
cameraView, // where you want to look at, in world space
cameraDir // Camera up direction (set to 0,-1,0 to look upside-down)
);
// Create out projection transform
mat4 projectionTransform = perspective(45.0f, (float)windowWidth / (float)windowHeight, 1.0f, 100.0f);
// Combine the world space to view space transformation matrix and the projection transformation matrix
mat4 worldToViewToProjectionTransform = projectionTransform * worldToViewTransform;
// Update the transforms in the shader program on the GPU
glUniformMatrix4fv(gWorldToViewToProjectionTransformLoc, 1, GL_FALSE, &worldToViewToProjectionTransform[0][0]);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(aitVertex), 0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(aitVertex), (const GLvoid*)12);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(aitVertex), (const GLvoid*)24);
// Set the material properties
glUniform1f(gKaLoc, 0.8f);
glUniform1f(gKdLoc, 0.8f);
// Bind the texture to the texture unit 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, gTextureObject[0]);
// Set our sampler to user Texture Unit 0
glUniform1i(gTextureSamplerLoc, 0);
// Draw triangle
mat4 modelToWorldTransform = mat4(1.0f);
static float angle = 0.0f;
angle+=1.0f;
modelToWorldTransform = rotate(modelToWorldTransform, angle, vec3(0.0f, 1.0f, 0.0f));
glUniformMatrix4fv(gModelToWorldTransformLoc, 1, GL_FALSE, &modelToWorldTransform[0][0]);
glDrawArrays(GL_TRIANGLES, 0, NUMVERTS);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
glutSwapBuffers();
}
This is the function that draws the earth onto the screen and determines where the camera is at.
void keyPressed (unsigned char key, int x, int y)
{
keyStates[key] = true; //Set the state of the current key to pressed
cout<<"keyPressed ";
}
void keyUp(unsigned char key, int x, int y)
{
keyStates[key] = false; //Set the state of the current key to released
cout<<"keyUp ";
}
void keyOperations (void)
{
if(keyStates['a'])
{
viewX += 0.5f;
}
cout<<"keyOperations ";
}
These are the functions I'm trying to use to edit the camera variables dynamically
// Create a vertex buffer
createVertexBuffer();
glutKeyboardFunc(keyPressed); //Tell Glut to use the method "keyPressed" for key events
glutKeyboardUpFunc(keyUp); //Tell Glut to use the method "keyUp" for key events
keyOperations();
glutMainLoop();
Finally here's the few lines in my main method where I'm trying to call the key press functions. In the console I see it detects that im pressing them but the planet doesnt move at all, I think I may be calling the keyOperations in the wrong place but I'm not sure.

Answer 1

You are correct, key operations is being called in the wrong place. Where it is now is called once then never again. It needs to go in your update code where you update the rotation of the planet. That way it is called at least once per frame.