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ALLEGRO_PRIM_ATTR(3) Library Functions Manual ALLEGRO_PRIM_ATTR(3) NAME ALLEGRO_PRIM_ATTR - Allegro 5 API SYNOPSIS #include <allegro5/allegro_primitives.h> typedef enum ALLEGRO_PRIM_ATTR DESCRIPTION Enumerates the types of vertex attributes that a custom vertex may have. • ALLEGRO_PRIM_POSITION - Position information, can be stored only in ALLEGRO_PRIM_SHORT_2, ALLEGRO_PRIM_FLOAT_2 and ALLEGRO_PRIM_FLOAT_3. • ALLEGRO_PRIM_COLOR_ATTR - Color information, stored in an ALLE- GRO_COLOR(3). The storage field of ALLEGRO_VERTEX_ELEMENT is ignored • 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). • 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. • ALLEGRO_PRIM_USER_ATTR - A user specified attribute. You can use any storage for this attribute. You may have at most ALLE- GRO_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 AL- LEGRO_PRIM_USER_ATTR + 1 and so on. To access these custom attributes from GLSL shaders you need to de- clare 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 pa- rameter 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 SEE ALSO ALLEGRO_VERTEX_DECL(3), ALLEGRO_PRIM_STORAGE(3), al_at- tach_shader_source(3) Allegro reference manual ALLEGRO_PRIM_ATTR(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO
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