Trying to implement Camera

Question

I'm trying to implement a Camera class in order to walk and look on the world as follow:

#ifndef _CAMERA_H_
#define _CAMERA_H_

#include <glm\glm.hpp>

class Camera
{
public:
    Camera();
    ~Camera();

    void Update(const glm::vec2& newXY);
    //if by = 0.0 it means, it will use the const Class speed to scale it
    void MoveForward(const float by = 0.0f);
    void MoveBackword(const float by = 0.0f);
    void MoveLef(const float by = 0.0f);
    void MoveRight(const float by = 0.0f);
    void MoveUp(const float by = 0.0f);
    void MoveDown(const float by = 0.0f);
    void Speed(const float speed = 0.0f);

    glm::vec3& GetCurrentPosition();
    glm::vec3& GetCurrentDirection();
    glm::mat4 GetWorldToView() const;
private:
    glm::vec3 position, viewDirection, strafeDir;
    glm::vec2 oldYX;

    float speed;
    const glm::vec3 up;
};

#endif

#include "Camera.h"
#include <glm\gtx\transform.hpp>

Camera::Camera()
    :up(0.0f, 1.0f, 0.0), viewDirection(0.0f, 0.0f, -1.0f),
    speed(0.1f)
{
}


Camera::~Camera()
{
}


void Camera::Update(const glm::vec2& newXY)
{
    glm::vec2 delta = newXY - oldYX;
    auto length = glm::length(delta);
    if (glm::length(delta) < 50.f)
    {
        strafeDir = glm::cross(viewDirection, up);
        glm::mat4 rotation = glm::rotate(-delta.x * speed, up) *
            glm::rotate(-delta.y * speed, strafeDir);

        viewDirection = glm::mat3(rotation) * viewDirection;
    }

    oldYX = newXY;
}

void Camera::Speed(const float speed)
{
    this->speed = speed;
}

void Camera::MoveForward(const float by)
{
    float s = by == 0.0f ? speed : by;

    position += s * viewDirection;
}
void Camera::MoveBackword(const float by)
{
    float s = by == 0.0f ? speed : by;

    position += -s * viewDirection;
}
void Camera::MoveLef(const float by )
{
    float s = by == 0.0f ? speed : by;
    position += -s * strafeDir;
}
void Camera::MoveRight(const float by )
{
    float s = by == 0.0f ? speed : by;
    position += -s * strafeDir;
}
void Camera::MoveUp(const float by )
{
    float s = by == 0.0f ? speed : by;
    position += s * up;
}
void Camera::MoveDown(const float by )
{
    float s = by == 0.0f ? speed : by;
    position += -s * up;
}

glm::vec3& Camera::GetCurrentPosition()
{
    return position;
}
glm::vec3& Camera::GetCurrentDirection()
{
    return viewDirection;
}

glm::mat4 Camera::GetWorldToView() const
{
    return glm::lookAt(position, position + viewDirection, up);
}

and I update and render as follow :

void Game::OnUpdate()
{
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);


    glUniformMatrix4fv(program->GetUniformLocation("modelToViewWorld"), 1, GL_FALSE, &cam.GetWorldToView()[0][0]);

}

void Game::OnRender()
{

    model->Draw();

}

Which the Vertix shader is:

#version 410

layout (location = 0) in vec3 inVertex;
layout (location = 1) in vec2 inTexture;
layout (location = 2) in vec3 inNormal;

uniform mat4 modelToViewWorld;


void main()
{
        gl_Position    = vec4(mat3(modelToViewWorld) * inVertex, 1);

}

But in result the model itslef is moving/rotating instead of moving the camera around the model. What am I doing wrong here?

Answer 1

Depending on the way your matrix type stores its values you may have to transpose the matrix to get the transformation right. You can use the boolean parameter of glUniformMatrix4fv(); to do that.

And the way you're applying the transformation in the vertex shader is omitting the translation part. Use it this way:

gl_Position = modelToViewWorld * vec4(inVertex, 1);