SPVertexData Class Reference

Inherits from	NSObject
Conforms to	NSCopying
Declared in	SPVertexData.h

Overview

The SPVertexData class manages a raw list of vertex information, allowing direct upload to OpenGL vertex buffers.

You only have to work with this class if you create display objects with a custom render function. If you don’t plan to do that, you can safely ignore it.

To render objects with OpenGL, you have to organize vertex data in so-called vertex buffers. Those buffers reside in graphics memory and can be accessed very efficiently by the GPU. Before you can move data into vertex buffers, you have to set it up in conventional memory - that is, in a byte array. That array contains all vertex information (the coordinates, color, and texture coordinates) - one vertex after the other.

To simplify creating and working with such a bulky list, the VertexData class was created. It contains methods to specify and modify vertex data. The raw array managed by the class can then easily be uploaded to a vertex buffer.

Premultiplied Alpha

The color values of texture files may contain premultiplied alpha values, which means that the RGB values were multiplied with the alpha value before saving them. On rendering, it makes a difference in which way the alpha value is saved; for that reason, the VertexData class mimics this behavior. You can choose how the alpha values should be handled via the premultipliedAlpha property.

Tasks

Initialization

– initWithSize:premultipliedAlpha:
Initializes a VertexData instance with a certain size. Designated Initializer.
– initWithSize:
Initializes a VertexData instance with a certain size, disabling premultiplied alpha.
– init
Initializes an empty VertexData object. Use the appendVertex: method and the numVertices property to change its size later.

Methods

– copyToVertexData:
Copies the vertex data of this instance to another vertex data object, starting at element 0.
– copyToVertexData:atIndex:
Copies the vertex data of this instance to another vertex data object, starting at a certain index.
– copyToVertexData:atIndex:numVertices:
Copies a range of vertices of this instance to another vertex data object.
– vertexAtIndex:
Returns a vertex at a certain position
– setVertex:atIndex:
Updates the vertex at a certain position.
– appendVertex:
Adds a vertex at the end, raising the number of vertices by one.
– positionAtIndex:
Returns the position of a vertex.
– setPosition:atIndex:
Updates the position of a vertex.
– setPositionWithX:y:atIndex:
Updates the position of a vertex.
– texCoordsAtIndex:
Returns the texture coordinates of a vertex.
– setTexCoords:atIndex:
Updates the texture coordinates of a vertex.
– setTexCoordsWithX:y:atIndex:
Updates the texture coordinates of a vertex.
– setColor:alpha:atIndex:
Updates the RGB color and the alpha value of a vertex.
– setColor:alpha:
Updates the RGB color and the alpha value of all vertices.
– colorAtIndex:
Returns the RGB color of a vertex (without premultiplied alpha).
– setColor:atIndex:
Sets the RGB color of a vertex. The method always expects non-premultiplied alpha values.
– setColor:
Sets the RGB color of all vertices at once. The method always expects non-premultiplied alpha values.
– alphaAtIndex:
Returns the alpha value of a vertex.
– setAlpha:atIndex:
Updates the alpha value of a vertex.
– setAlpha:
Updates the alpha value of all vertices.
– scaleAlphaBy:
Multiplies all alpha values with a certain factor.
– scaleAlphaBy:atIndex:numVertices:
Multiplies a range of alpha values with a certain factor.
– setPremultipliedAlpha:updateVertices:
Changes the way alpha and color values are stored. Optionally, all exisiting vertices are updated.
– transformVerticesWithMatrix:atIndex:numVertices:
Transforms the positions of subsequent vertices by multiplication with a transformation matrix.
– bounds
Calculates the bounding rectangle of all vertices.
– boundsAfterTransformation:
Calculates the bounding rectangle of all vertices after being transformed by a matrix.
– boundsAfterTransformation:atIndex:numVertices:
Calculates the bounding rectangle of subsequent vertices after being transformed by a matrix.

Properties

vertices
Returns a pointer to the raw vertex data.
property
numVertices
Indicates the size of the VertexData object. You can resize the object any time; if you make it bigger, it will be filled up with vertices that have all properties zeroed, except for the alpha value (it’s 1).
property
premultipliedAlpha
Indicates if the rgb values are stored premultiplied with the alpha value. If you change this property, all color data will be updated accordingly.
property
tinted
Indicates if any vertices have a non-white color or are not fully opaque.
property

Properties

numVertices

Indicates the size of the VertexData object. You can resize the object any time; if you make it bigger, it will be filled up with vertices that have all properties zeroed, except for the alpha value (it’s 1).

@property (nonatomic, assign) int numVertices

Discussion

Declared In

SPVertexData.h

premultipliedAlpha

Indicates if the rgb values are stored premultiplied with the alpha value. If you change this property, all color data will be updated accordingly.

@property (nonatomic, assign) BOOL premultipliedAlpha

Discussion

Indicates if the rgb values are stored premultiplied with the alpha value. If you change this property, all color data will be updated accordingly.

Declared In

SPVertexData.h

tinted

Indicates if any vertices have a non-white color or are not fully opaque.

@property (nonatomic, readonly) BOOL tinted

Discussion

Indicates if any vertices have a non-white color or are not fully opaque.

Declared In

SPVertexData.h

vertices

Returns a pointer to the raw vertex data.

@property (nonatomic, readonly) SPVertex *vertices

Discussion

Returns a pointer to the raw vertex data.

Declared In

SPVertexData.h

Instance Methods

alphaAtIndex:

Returns the alpha value of a vertex.

- (float)alphaAtIndex:(int)index

Discussion

Returns the alpha value of a vertex.

Declared In

SPVertexData.h

appendVertex:

Adds a vertex at the end, raising the number of vertices by one.

- (void)appendVertex:(SPVertex)vertex

Discussion

Adds a vertex at the end, raising the number of vertices by one.

Declared In

SPVertexData.h

bounds

Calculates the bounding rectangle of all vertices.

- (SPRectangle *)bounds

Discussion

Calculates the bounding rectangle of all vertices.

Declared In

SPVertexData.h

boundsAfterTransformation:

Calculates the bounding rectangle of all vertices after being transformed by a matrix.

- (SPRectangle *)boundsAfterTransformation:(SPMatrix *)matrix

Discussion

Calculates the bounding rectangle of all vertices after being transformed by a matrix.

Declared In

SPVertexData.h

boundsAfterTransformation:atIndex:numVertices:

Calculates the bounding rectangle of subsequent vertices after being transformed by a matrix.

- (SPRectangle *)boundsAfterTransformation:(SPMatrix *)matrix atIndex:(int)index numVertices:(int)count

Discussion

Calculates the bounding rectangle of subsequent vertices after being transformed by a matrix.

Declared In

SPVertexData.h

colorAtIndex:

Returns the RGB color of a vertex (without premultiplied alpha).

- (uint)colorAtIndex:(int)index

Discussion

Returns the RGB color of a vertex (without premultiplied alpha).

Declared In

SPVertexData.h

copyToVertexData:

Copies the vertex data of this instance to another vertex data object, starting at element 0.

- (void)copyToVertexData:(SPVertexData *)target

Discussion

Copies the vertex data of this instance to another vertex data object, starting at element 0.

Declared In

SPVertexData.h

copyToVertexData:atIndex:

Copies the vertex data of this instance to another vertex data object, starting at a certain index.

- (void)copyToVertexData:(SPVertexData *)target atIndex:(int)targetIndex

Discussion

Copies the vertex data of this instance to another vertex data object, starting at a certain index.

Declared In

SPVertexData.h

copyToVertexData:atIndex:numVertices:

Copies a range of vertices of this instance to another vertex data object.

- (void)copyToVertexData:(SPVertexData *)target atIndex:(int)targetIndex numVertices:(int)count

Discussion

Copies a range of vertices of this instance to another vertex data object.

Declared In

SPVertexData.h

init

Initializes an empty VertexData object. Use the appendVertex: method and the numVertices property to change its size later.

- (instancetype)init

Discussion

Initializes an empty VertexData object. Use the appendVertex: method and the numVertices property to change its size later.

Declared In

SPVertexData.h

initWithSize:

Initializes a VertexData instance with a certain size, disabling premultiplied alpha.

- (instancetype)initWithSize:(int)numVertices

Discussion

Initializes a VertexData instance with a certain size, disabling premultiplied alpha.

Declared In

SPVertexData.h

initWithSize:premultipliedAlpha:

Initializes a VertexData instance with a certain size. Designated Initializer.

- (instancetype)initWithSize:(int)numVertices premultipliedAlpha:(BOOL)pma

Discussion

Initializes a VertexData instance with a certain size. Designated Initializer.

Declared In

SPVertexData.h

positionAtIndex:

Returns the position of a vertex.

- (SPPoint *)positionAtIndex:(int)index

Discussion

Returns the position of a vertex.

Declared In

SPVertexData.h

scaleAlphaBy:

Multiplies all alpha values with a certain factor.

- (void)scaleAlphaBy:(float)factor

Discussion

Multiplies all alpha values with a certain factor.

Declared In

SPVertexData.h

scaleAlphaBy:atIndex:numVertices:

Multiplies a range of alpha values with a certain factor.

- (void)scaleAlphaBy:(float)factor atIndex:(int)index numVertices:(int)count

Discussion

Multiplies a range of alpha values with a certain factor.

Declared In

SPVertexData.h

setAlpha:

Updates the alpha value of all vertices.

- (void)setAlpha:(float)alpha

Discussion

Updates the alpha value of all vertices.

Declared In

SPVertexData.h

setAlpha:atIndex:

Updates the alpha value of a vertex.

- (void)setAlpha:(float)alpha atIndex:(int)index

Discussion

Updates the alpha value of a vertex.

Declared In

SPVertexData.h

setColor:

Sets the RGB color of all vertices at once. The method always expects non-premultiplied alpha values.

- (void)setColor:(uint)color

Discussion

Sets the RGB color of all vertices at once. The method always expects non-premultiplied alpha values.

Declared In

SPVertexData.h

setColor:alpha:

Updates the RGB color and the alpha value of all vertices.

- (void)setColor:(uint)color alpha:(float)alpha

Discussion

Updates the RGB color and the alpha value of all vertices.

Declared In

SPVertexData.h

setColor:alpha:atIndex:

Updates the RGB color and the alpha value of a vertex.

- (void)setColor:(uint)color alpha:(float)alpha atIndex:(int)index

Discussion

Updates the RGB color and the alpha value of a vertex.

Declared In

SPVertexData.h

setColor:atIndex:

Sets the RGB color of a vertex. The method always expects non-premultiplied alpha values.

- (void)setColor:(uint)color atIndex:(int)index

Discussion

Sets the RGB color of a vertex. The method always expects non-premultiplied alpha values.

Declared In

SPVertexData.h

setPosition:atIndex:

Updates the position of a vertex.

- (void)setPosition:(SPPoint *)position atIndex:(int)index

Discussion

Updates the position of a vertex.

Declared In

SPVertexData.h

setPositionWithX:y:atIndex:

Updates the position of a vertex.

- (void)setPositionWithX:(float)x y:(float)y atIndex:(int)index

Discussion

Updates the position of a vertex.

Declared In

SPVertexData.h

setPremultipliedAlpha:updateVertices:

Changes the way alpha and color values are stored. Optionally, all exisiting vertices are updated.

- (void)setPremultipliedAlpha:(BOOL)value updateVertices:(BOOL)update

Discussion

Changes the way alpha and color values are stored. Optionally, all exisiting vertices are updated.

Declared In

SPVertexData.h

setTexCoords:atIndex:

Updates the texture coordinates of a vertex.

- (void)setTexCoords:(SPPoint *)texCoords atIndex:(int)index

Discussion

Updates the texture coordinates of a vertex.

Declared In

SPVertexData.h

setTexCoordsWithX:y:atIndex:

Updates the texture coordinates of a vertex.

- (void)setTexCoordsWithX:(float)x y:(float)y atIndex:(int)index

Discussion

Updates the texture coordinates of a vertex.

Declared In

SPVertexData.h

setVertex:atIndex:

Updates the vertex at a certain position.

- (void)setVertex:(SPVertex)vertex atIndex:(int)index

Discussion

Updates the vertex at a certain position.

Declared In

SPVertexData.h

texCoordsAtIndex:

Returns the texture coordinates of a vertex.

- (SPPoint *)texCoordsAtIndex:(int)index

Discussion

Returns the texture coordinates of a vertex.

Declared In

SPVertexData.h

transformVerticesWithMatrix:atIndex:numVertices:

Transforms the positions of subsequent vertices by multiplication with a transformation matrix.

- (void)transformVerticesWithMatrix:(SPMatrix *)matrix atIndex:(int)index numVertices:(int)count

Discussion

Transforms the positions of subsequent vertices by multiplication with a transformation matrix.

Declared In

SPVertexData.h

vertexAtIndex:

Returns a vertex at a certain position

- (SPVertex)vertexAtIndex:(int)index

Discussion

Returns a vertex at a certain position

Declared In

SPVertexData.h