# Scaling and translation

We are starting from the easist scale transform

## include glm header 

in main.cpp, add the header files of glm.hpp

```cpp
#define GLM_ENABLE_EXPERIMENTAL
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtx/transform.hpp>
```

## Generate the scale matrix

Here we are scaling the triangles by a factor of 0.5

```cpp
    glm::mat4 mat_scale = glm::scale(  // Scale first
        glm::mat4(1.0),              // identity matrix
        glm::vec3( 0.5f, 0.5f, 0.5f )
    );
```

## Change colour.vert

in the vertex shader colour.vert, declare a uniform for model transformation

```glsl
// transformation in the world and camera space
uniform mat4 modelview;
```

Transoform the vertex position using the matrix

```glsl
void main()
{
    gl_Position = modelview * vec4(pos, 1.0); 
    colour_vert = colour_in;
}
```

## share variable with GPU using **uniform** &#x20;

In initTriangle() in main.cpp, connect it with the modelview matrix created by GLM

```cpp
    glm::mat4 mat_modelview = mat_scale;
    
    GLuint modelview_loc = glGetUniformLocation( shader.program, "modelview" );
    glUniformMatrix4fv(modelview_loc, 1, GL_FALSE, &mat_modelview[0][0]);
```

Now we get

<figure><img src="https://3464970502-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F3JUKGJZ67JX02QZdPhsy%2Fuploads%2FP8oKXrVQ4f5o4AZbjQ8M%2Fimage.png?alt=media&#x26;token=83b0af41-c546-4bf6-b28c-de978e7fc1ca" alt=""><figcaption></figcaption></figure>

## Translation

We can also translate the scaled model, for example 0.3 on X and 0.2 on Y

```cpp
    glm::mat4 mat_scale = glm::scale(glm::vec3(0.5f, 0.5f, 0.5f));
    glm::mat4 mat_trans = glm::translate(glm::vec3(0.3f, 0.2f, 0.0f));

    glm::mat4 mat_modelview = mat_trans * mat_scale;
```

<figure><img src="https://3464970502-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F3JUKGJZ67JX02QZdPhsy%2Fuploads%2FmaejxoG1opxE9TJNfTR1%2Fimage.png?alt=media&#x26;token=f9e707af-7f1c-4f81-b579-ef07dc34555d" alt=""><figcaption></figcaption></figure>