ALLEGRO_PRIM_ATTR - Allegro 5 API
#include <allegro5/allegro_primitives.h> typedef enum ALLEGRO_PRIM_ATTR
Enumerates the types of vertex attributes that a custom vertex may have.
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ALLEGRO_PRIM_POSITION - Position information, can be stored only in ALLEGRO_PRIM_SHORT_2, ALLEGRO_PRIM_FLOAT_2 and ALLEGRO_PRIM_FLOAT_3. | ||
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ALLEGRO_PRIM_COLOR_ATTR - Color information, stored in an ALLEGRO_COLOR(3). The storage field of ALLEGRO_VERTEX_ELEMENT is ignored | ||
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ALLEGRO_PRIM_TEX_COORD - Texture coordinate information, can be stored only in ALLEGRO_PRIM_FLOAT_2 and ALLEGRO_PRIM_SHORT_2. These coordinates are normalized by the width and height of the texture, meaning that the bottom-right corner has texture coordinates of (1, 1). | ||
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ALLEGRO_PRIM_TEX_COORD_PIXEL - Texture coordinate information, can be stored only in ALLEGRO_PRIM_FLOAT_2 and ALLEGRO_PRIM_SHORT_2. These coordinates are measured in pixels. | ||
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ALLEGRO_PRIM_USER_ATTR - A user specified attribute. You can use any storage for this attribute. You may have at most ALLEGRO_PRIM_MAX_USER_ATTR (currently 10) of these that you can specify by adding an index to the value of ALLEGRO_PRIM_USER_ATTR, e.g. the first user attribute is ALLEGRO_PRIM_USER_ATTR + 0, the second is ALLEGRO_PRIM_USER_ATTR + 1 and so on. |
To access these custom attributes from GLSL shaders you need to declare attributes that follow this nomenclature: al_user_attr_# where # is the index of the attribute.
For example to have a position and a normal vector for each vertex you could declare it like this:
ALLEGRO_VERTEX_ELEMENT elements[3] = {
{ALLEGRO_PRIM_POSITION, ALLEGRO_PRIM_FLOAT_3, 0},
{ALLEGRO_PRIM_USER_ATTR + 0, ALLEGRO_PRIM_FLOAT_3, 12},
{0, 0, 0}};
And then in your vertex shader access it like this:
attribute vec3 al_pos; // ALLEGRO_PRIM_POSITION
attribute vec3 al_user_attr_0; // ALLEGRO_PRIM_USER_ATTR + 0
varying float light;
const vec3 light_direction = vec3(0, 0, 1);
void main() {
light = dot(al_user_attr_0, light_direction);
gl_Position = al_pos;
}
To access these custom attributes from HLSL you need to declare a parameter with the following semantics: TEXCOORD{# + 2} where # is the index of the attribute. E.g. the first attribute can be accessed via TEXCOORD2, second via TEXCOORD3 and so on.
Since: 5.1.6
ALLEGRO_VERTEX_DECL(3), ALLEGRO_PRIM_STORAGE(3), al_attach_shader_source(3)