Struct Attribute

pub struct Attribute(/* private fields */);

Implementations

impl Attribute

pub fn new( attribute_buffer: &AttributeBuffer, name: &str, stride: usize, offset: usize, components: i32, type_: AttributeType, ) -> Attribute

Describes the layout for a list of vertex attribute values (For example, a list of texture coordinates or colors).

The name is used to access the attribute inside a GLSL vertex shader and there are some special names you should use if they are applicable: <itemizedlist> <listitem>“cogl_position_in” (used for vertex positions)</listitem> <listitem>“cogl_color_in” (used for vertex colors)</listitem> <listitem>“cogl_tex_coord0_in”, “cogl_tex_coord1”, … (used for vertex texture coordinates)</listitem> <listitem>“cogl_normal_in” (used for vertex normals)</listitem> <listitem>“cogl_point_size_in” (used to set the size of points per-vertex. Note this can only be used if COGL_FEATURE_ID_POINT_SIZE_ATTRIBUTE is advertised and Pipeline::set_per_vertex_point_size is called on the pipeline. </listitem> </itemizedlist>

The attribute values corresponding to different vertices can either be tightly packed or interleaved with other attribute values. For example it’s common to define a structure for a single vertex like:

typedef struct
{
  float x, y, z; /<!-- -->* position attribute *<!-- -->/
  float s, t; /<!-- -->* texture coordinate attribute *<!-- -->/
} MyVertex;

And then create an array of vertex data something like:

MyVertex vertices[100] = { .... }

In this case, to describe either the position or texture coordinate attribute you have to move <literal>sizeof (MyVertex)</literal> bytes to move from one vertex to the next. This is called the attribute stride. If you weren’t interleving attributes and you instead had a packed array of float x, y pairs then the attribute stride would be <literal>(2 * sizeof (float))</literal>. So the stride is the number of bytes to move to find the attribute value of the next vertex.

Normally a list of attributes starts at the beginning of an array. So for the <literal>MyVertex</literal> example above the offset is the offset inside the <literal>MyVertex</literal> structure to the first component of the attribute. For the texture coordinate attribute the offset would be <literal>offsetof (MyVertex, s)</literal> or instead of using the offsetof macro you could use <literal>sizeof (float) * 3</literal>. If you’ve divided your array into blocks of non-interleved attributes then you will need to calculate the offset as the number of bytes in blocks preceding the attribute you’re describing.

An attribute often has more than one component. For example a color is often comprised of 4 red, green, blue and alpha components, and a position may be comprised of 2 x and y components. You should aim to keep the number of components to a minimum as more components means more data needs to be mapped into the GPU which can be a bottlneck when dealing with a large number of vertices.

Finally you need to specify the component data type. Here you should aim to use the smallest type that meets your precision requirements. Again the larger the type then more data needs to be mapped into the GPU which can be a bottlneck when dealing with a large number of vertices.

attribute_buffer

The AttributeBuffer containing the actual attribute data

name

The name of the attribute (used to reference it from GLSL)

stride

The number of bytes to jump to get to the next attribute value for the next vertex. (Usually <literal>sizeof (MyVertex)</literal>)

offset

The byte offset from the start of attribute_buffer for the first attribute value. (Usually <literal>offsetof (MyVertex, component0)</literal>

components

The number of components (e.g. 4 for an rgba color or 3 for and (x,y,z) position)

type_

FIXME

Returns

A newly allocated Attribute describing the layout for a list of attribute values stored in array.

pub fn new_const_1f(context: &Context, name: &str, value: f32) -> Attribute

Creates a new, single component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constant value is a single precision floating point scalar which should have a corresponding declaration in GLSL code like:

[| attribute float name; |]

context

A Context

name

The name of the attribute (used to reference it from GLSL)

value

The constant value for the attribute

Returns

A newly allocated Attribute representing the given constant value.

pub fn new_const_2f( context: &Context, name: &str, component0: f32, component1: f32, ) -> Attribute

Creates a new, 2 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (component0, component1) represent a 2 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec2 name; |]

context

A Context

name

The name of the attribute (used to reference it from GLSL)

component0

The first component of a 2 component vector

component1

The second component of a 2 component vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_2fv( context: &Context, name: &str, value: &[f32; 2], ) -> Attribute

Creates a new, 2 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (value[0], value[1]) represent a 2 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec2 name; |]

context

A Context

name

The name of the attribute (used to reference it from GLSL)

value

A pointer to a 2 component float vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_2x2fv( context: &Context, name: &str, matrix2x2: &[f32; 4], transpose: bool, ) -> Attribute

Creates a new matrix attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

matrix2x2 represent a square 2 by 2 matrix specified in column-major order (each pair of consecutive numbers represents a column) which should have a corresponding declaration in GLSL code like:

[| attribute mat2 name; |]

If transpose is true then all matrix components are rotated around the diagonal of the matrix such that the first column becomes the first row and the second column becomes the second row.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

matrix2x2

A pointer to a 2 by 2 matrix

transpose

Whether the matrix should be transposed on upload or not

Returns

A newly allocated Attribute representing the given constant matrix.

pub fn new_const_3f( context: &Context, name: &str, component0: f32, component1: f32, component2: f32, ) -> Attribute

Creates a new, 3 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (component0, component1, component2) represent a 3 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec3 name; |]

unless the built in name “cogl_normal_in” is being used where no explicit GLSL declaration need be made.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

component0

The first component of a 3 component vector

component1

The second component of a 3 component vector

component2

The third component of a 3 component vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_3fv( context: &Context, name: &str, value: &[f32; 3], ) -> Attribute

Creates a new, 3 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (value[0], value[1], value[2]) represent a 3 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec3 name; |]

unless the built in name “cogl_normal_in” is being used where no explicit GLSL declaration need be made.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

value

A pointer to a 3 component float vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_3x3fv( context: &Context, name: &str, matrix3x3: &[f32; 9], transpose: bool, ) -> Attribute

Creates a new matrix attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

matrix3x3 represent a square 3 by 3 matrix specified in column-major order (each triple of consecutive numbers represents a column) which should have a corresponding declaration in GLSL code like:

[| attribute mat3 name; |]

If transpose is true then all matrix components are rotated around the diagonal of the matrix such that the first column becomes the first row and the second column becomes the second row etc.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

matrix3x3

A pointer to a 3 by 3 matrix

transpose

Whether the matrix should be transposed on upload or not

Returns

A newly allocated Attribute representing the given constant matrix.

pub fn new_const_4f( context: &Context, name: &str, component0: f32, component1: f32, component2: f32, component3: f32, ) -> Attribute

Creates a new, 4 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (component0, component1, component2, constant3) represent a 4 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec4 name; |]

unless one of the built in names “cogl_color_in”, “cogl_tex_coord0_in or “cogl_tex_coord1_in” etc is being used where no explicit GLSL declaration need be made.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

component0

The first component of a 4 component vector

component1

The second component of a 4 component vector

component2

The third component of a 4 component vector

component3

The fourth component of a 4 component vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_4fv( context: &Context, name: &str, value: &[f32; 4], ) -> Attribute

Creates a new, 4 component, attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

The constants (value[0], value[1], value[2], value[3]) represent a 4 component float vector which should have a corresponding declaration in GLSL code like:

[| attribute vec4 name; |]

unless one of the built in names “cogl_color_in”, “cogl_tex_coord0_in or “cogl_tex_coord1_in” etc is being used where no explicit GLSL declaration need be made.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

value

A pointer to a 4 component float vector

Returns

A newly allocated Attribute representing the given constant vector.

pub fn new_const_4x4fv( context: &Context, name: &str, matrix4x4: &[f32; 16], transpose: bool, ) -> Attribute

Creates a new matrix attribute whose value remains constant across all the vertices of a primitive without needing to duplicate the value for each vertex.

matrix4x4 represent a square 4 by 4 matrix specified in column-major order (each 4-tuple of consecutive numbers represents a column) which should have a corresponding declaration in GLSL code like:

[| attribute mat4 name; |]

If transpose is true then all matrix components are rotated around the diagonal of the matrix such that the first column becomes the first row and the second column becomes the second row etc.

context

A Context

name

The name of the attribute (used to reference it from GLSL)

matrix4x4

A pointer to a 4 by 4 matrix

transpose

Whether the matrix should be transposed on upload or not

Returns

A newly allocated Attribute representing the given constant matrix.

pub fn get_buffer(&self) -> Option<AttributeBuffer>

Returns

the AttributeBuffer that was set with Attribute::set_buffer or Attribute::new.

pub fn get_normalized(&self) -> bool

Returns

the value of the normalized property set with Attribute::set_normalized.

pub fn set_buffer(&self, attribute_buffer: &AttributeBuffer)

Sets a new AttributeBuffer for the attribute.

attribute_buffer

A AttributeBuffer

pub fn set_normalized(&self, normalized: bool)

Sets whether fixed point attribute types are mapped to the range 0→1. For example when this property is TRUE and a AttributeType::UnsignedByte type is used then the value 255 will be mapped to 1.0.

The default value of this property depends on the name of the attribute. For the builtin properties cogl_color_in and cogl_normal_in it will default to TRUE and for all other names it will default to FALSE.

normalized

The new value for the normalized property.

Trait Implementations

impl Clone for Attribute

fn clone(&self) -> Attribute

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Attribute

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Attribute

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for Attribute

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Attribute

fn cmp(&self, other: &Attribute) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T: ObjectType> PartialEq<T> for Attribute

fn eq(&self, other: &T) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: ObjectType> PartialOrd<T> for Attribute

fn partial_cmp(&self, other: &T) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for Attribute

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for Attribute

impl IsA<Object> for Attribute