## Primitives

Primitives — Functions that draw various primitive 3D shapes

## Synopsis

    void                cogl_rectangle                      (float x_1,
                                                             float y_1,
                                                             float x_2,
                                                             float y_2);
    void                cogl_rectangles                     (const float *verts,
                                                             unsigned int n_rects);
    void                cogl_rectangle_with_texture_coords  (float x1,
                                                             float y1,
                                                             float x2,
                                                             float y2,
                                                             float tx1,
                                                             float ty1,
                                                             float tx2,
                                                             float ty2);
    void                cogl_rectangles_with_texture_coords (const float *verts,
                                                             unsigned int n_rects);
    void                cogl_rectangle_with_multitexture_coords
                                                            (float x1,
                                                             float y1,
                                                             float x2,
                                                             float y2,
                                                             const float *tex_coords,
                                                             int tex_coords_len);
    void                cogl_polygon                        (const CoglTextureVertex *vertices,
                                                             unsigned int n_vertices,
                                                             gboolean use_color);

## Description

The primitives API provides utilities for drawing some common 3D shapes in a more convenient way than the CoglVertexBuffer API provides.

## Details

### cogl_rectangle ()

    void                cogl_rectangle                      (float x_1,
                                                             float y_1,
                                                             float x_2,
                                                             float y_2);

Fills a rectangle at the given coordinates with the current source material

`x_1` : | X coordinate of the top-left corner
`y_1` : | Y coordinate of the top-left corner
`x_2` : | X coordinate of the bottom-right corner
`y_2` : | Y coordinate of the bottom-right corner

### cogl_rectangles ()

    void                cogl_rectangles                     (const float *verts,
                                                             unsigned int n_rects);

Draws a series of rectangles in the same way that `cogl_rectangle()` does. In some situations it can give a significant performance boost to use this function rather than calling `cogl_rectangle()` separately for each rectangle.

`verts` should point to an array of floats with `n_rects` * 4 elements. Each group of 4 values corresponds to the parameters x1, y1, x2, and y2, and have the same meaning as in `cogl_rectangle()`.

`verts` : | an array of vertices. [in][array][transfer none]
`n_rects` : | number of rectangles to draw

Since 1.0

### cogl_rectangle_with_texture_coords ()

    void                cogl_rectangle_with_texture_coords  (float x1,
                                                             float y1,
                                                             float x2,
                                                             float y2,
                                                             float tx1,
                                                             float ty1,
                                                             float tx2,
                                                             float ty2);

Draw a rectangle using the current material and supply texture coordinates to be used for the first texture layer of the material. To draw the entire texture pass in `tx1`=0.0 `ty1`=0.0 `tx2`=1.0 `ty2`=1.0.

`x1` : | x coordinate upper left on screen.
`y1` : | y coordinate upper left on screen.
`x2` : | x coordinate lower right on screen.
`y2` : | y coordinate lower right on screen.
`tx1` : | x part of texture coordinate to use for upper left pixel
`ty1` : | y part of texture coordinate to use for upper left pixel
`tx2` : | x part of texture coordinate to use for lower right pixel
`ty2` : | y part of texture coordinate to use for left pixel

Since 1.0

### cogl_rectangles_with_texture_coords ()

    void                cogl_rectangles_with_texture_coords (const float *verts,
                                                             unsigned int n_rects);

Draws a series of rectangles in the same way that `cogl_rectangle_with_texture_coords()` does. In some situations it can give a significant performance boost to use this function rather than calling `cogl_rectangle_with_texture_coords()` separately for each rectangle.

`verts` should point to an array of floats with `n_rects` * 8 elements. Each group of 8 values corresponds to the parameters x1, y1, x2, y2, tx1, ty1, tx2 and ty2 and have the same meaning as in `cogl_rectangle_with_texture_coords()`.

`verts` : | an array of vertices. [in][array][transfer none]
`n_rects` : | number of rectangles to draw

Since 0.8.6

### cogl_rectangle_with_multitexture_coords ()

    void                cogl_rectangle_with_multitexture_coords
                                                            (float x1,
                                                             float y1,
                                                             float x2,
                                                             float y2,
                                                             const float *tex_coords,
                                                             int tex_coords_len);

This function draws a rectangle using the current source material to texture or fill with. As a material may contain multiple texture layers this interface lets you supply texture coordinates for each layer of the material.

The first pair of coordinates are for the first layer (with the smallest layer index) and if you supply less texture coordinates than there are layers in the current source material then default texture coordinates (0.0, 0.0, 1.0, 1.0) are generated.

`x1` : | x coordinate upper left on screen.
`y1` : | y coordinate upper left on screen.
`x2` : | x coordinate lower right on screen.
`y2` : | y coordinate lower right on screen.
`tex_coords` : | An array containing groups of 4 float values: [tx1, ty1, tx2, ty2] that are interpreted as two texture coordinates; one for the upper left texel, and one for the lower right texel. Each value should be between 0.0 and 1.0, where the coordinate (0.0, 0.0) represents the top left of the texture, and (1.0, 1.0) the bottom right. [in][array][transfer none]
`tex_coords_len` : | The length of the tex_coords array. (e.g. for one layer and one group of texture coordinates, this would be 4)

Since 1.0

### cogl_polygon ()

    void                cogl_polygon                        (const CoglTextureVertex *vertices,
                                                             unsigned int n_vertices,
                                                             gboolean use_color);

Draws a convex polygon using the current source material to fill / texture with according to the texture coordinates passed.

If `use_color` is `TRUE` then the color will be changed for each vertex using the value specified in the color member of CoglTextureVertex. This can be used for example to make the texture fade out by setting the alpha value of the color.

All of the texture coordinates must be in the range [0,1] and repeating the texture is not supported.

Because of the way this function is implemented it will currently only work if either the texture is not sliced or the backend is not OpenGL ES and the minifying and magnifying functions are both set to COGL_MATERIAL_FILTER_NEAREST.

`vertices` : | An array of CoglTextureVertex structs
`n_vertices` : | The length of the vertices array
`use_color` : | `TRUE` if the color member of CoglTextureVertex should be used

Since 1.0