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glextensions - GL_EXT_geometry_shader4.wiki

Dependencies
Overview
New Procedures and Functions
New Tokens
Errors
New State
New Implementation Dependent State

Dependencies

OpenGL 1.1 is required.

This extension is written against the OpenGL 2.0 specification.

GL_EXT_framebuffer_object interacts with this extension.

GL_EXT_framebuffer_blit interacts with this extension.

GL_EXT_texture_array interacts with this extension.

GL_ARB_texture_rectangle trivially affects the definition of this extension.

GL_EXT_texture_buffer_object trivially affects the definition of this extension.

GL_NV_primitive_restart trivially affects the definition of this extension.

This extension interacts with GL_EXT_transform_feedback.

Overview

EXT_geometry_shader4 defines a new shader type available to be run on the GPU, called a geometry shader. Geometry shaders are run after vertices are transformed, but prior to color clamping, flat shading and clipping.

A geometry shader begins with a single primitive (point, line, triangle). It can read the attributes of any of the vertices in the primitive and use them to generate new primitives. A geometry shader has a fixed output primitive type (point, line strip, or triangle strip) and emits vertices to define a new primitive. A geometry shader can emit multiple disconnected primitives. The primitives emitted by the geometry shader are clipped and then processed like an equivalent OpenGL primitive specified by the application.

Furthermore, EXT_geometry_shader4 provides four additional primitive types: lines with adjacency, line strips with adjacency, separate triangles with adjacency, and triangle strips with adjacency. Some of the vertices specified in these new primitive types are not part of the ordinary primitives, instead they represent neighboring vertices that are adjacent to the two line segment end points (lines/strips) or the three triangle edges (triangles/tstrips). These vertices can be accessed by geometry shaders and used to match up the vertices emitted by the geometry shader with those of neighboring primitives.

Since geometry shaders expect a specific input primitive type, an error will occur if the application presents primitives of a different type. For example, if a geometry shader expects points, an error will occur at Begin() time, if a primitive mode of TRIANGLES is specified.

New Procedures and Functions

void ProgramParameteriEXT(uint program, enum pname, int value); void FramebufferTextureEXT(enum target, enum attachment, uint texture, int level); void FramebufferTextureLayerEXT(enum target, enum attachment, uint texture, int level, int layer); void FramebufferTextureFaceEXT(enum target, enum attachment, uint texture, int level, enum face);

New Tokens

Accepted by the

<type>

parameter of CreateShader and returned by the

parameter of GetShaderiv:

|GEOMETRY_SHADER_EXT | 0x8DD9| |:--------------------------|:----------|

Accepted by the

<pname>

parameter of ProgramParameteriEXT and GetProgramiv:

|GEOMETRY_VERTICES_OUT_EXT | 0x8DDA| |:----------------------------|:--------------| |GEOMETRY_INPUT_TYPE_EXT | 0x8DDB | |GEOMETRY_OUTPUT_TYPE_EXT | 0x8DDC |

Accepted by the

<pname>

parameter of GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev:

|MAX_GEOMETRY_TEXTURE_IMAGE_UNITS_EXT | 0x8C29| |:------------------------------------------------|:----------| |MAX_GEOMETRY_VARYING_COMPONENTS_EXT | 0x8DDD| |MAX_VERTEX_VARYING_COMPONENTS_EXT | 0x8DDE| |MAX_VARYING_COMPONENTS_EXT | 0x8B4B| |MAX_GEOMETRY_UNIFORM_COMPONENTS_EXT | 0x8DDF| |MAX_GEOMETRY_OUTPUT_VERTICES_EXT | 0x8DE0| |MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS_EXT | 0x8DE1|

Accepted by the

<mode>

parameter of Begin, DrawArrays, MultiDrawArrays, DrawElements, MultiDrawElements, and DrawRangeElements:

|LINES_ADJACENCY_EXT | 0xA| |:-------------------------------------------|:---------| |LINE_STRIP_ADJACENCY_EXT | 0xB| |TRIANGLES_ADJACENCY_EXT | 0xC| |TRIANGLE_STRIP_ADJACENCY_EXT | 0xD|

Returned by CheckFramebufferStatusEXT:

|FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS_EXT | 0x8DA8| |:------------------------------------------------|:---------| |FRAMEBUFFER_INCOMPLETE_LAYER_COUNT_EXT | 0x8DA9|

Accepted by the

<pname>

parameter of GetFramebufferAttachmentParameterivEXT:

|FRAMEBUFFER_ATTACHMENT_LAYERED_EXT | 0x8DA7| |:----------------------------------------------|:----------| |FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT | 0x8CD4|

Accepted by the

<cap>

parameter of Enable, Disable, and IsEnabled, and by the

<pname>

parameter of GetIntegerv, GetFloatv, GetDoublev, and GetBooleanv:

|PROGRAM_POINT_SIZE_EXT | 0x8642| |:----------------------------------|:----------------------|

(Note: FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT is simply an alias for the FRAMEBUFFER_ATTACHMENT_TEXTURE_3D_ZOFFSET_EXT token provided in GL_EXT_framebuffer_object. This extension generalizes the notion of "

" to include layers of an array texture.)

(Note: PROGRAM_POINT_SIZE_EXT is simply an alias for the VERTEX_PROGRAM_POINT_SIZE token provided in OpenGL 2.0, which is itself an alias for VERTEX_PROGRAM_POINT_SIZE_ARB provided by GL_ARB_vertex_program. Program-computed point sizes can be enabled if geometry shaders are enabled.)