QSGGeometry ¶

概要 ¶

详细描述 ¶

QSGGeometry class stores the geometry of the primitives rendered with the scene graph. It contains vertex data and optionally index data. The mode used to draw the geometry is specified with setDrawingMode() , which maps directly to the graphics API’s drawing mode, such as GL_TRIANGLE_STRIP , GL_TRIANGLES ，或 GL_POINTS in case of OpenGL.

Vertices can be as simple as points defined by x and y values or can be more complex where each vertex contains a normal, texture coordinates and a 3D position. The AttributeSet is used to describe how the vertex data is built up. The attribute set can only be specified on construction. The QSGGeometry class provides a few convenience attributes and attribute sets by default. The defaultAttributes_Point2D() function returns an attribute set to be used in normal solid color rectangles, while the defaultAttributes_TexturedPoint2D function returns attributes to be used for textured 2D geometry. The vertex data is internally stored as a void * and is accessible with the vertexData() function. Convenience accessors for the common attribute sets are available with vertexDataAsPoint2D() and vertexDataAsTexturedPoint2D() . Vertex data is allocated by passing a vertex count to the constructor or by calling allocate() later.

QSGGeometry can optionally contain indices of either unsigned 32-bit, unsigned 16-bit, or unsigned 8-bit integers. The index type must be specified during construction and cannot be changed.

Below is a snippet illustrating how a geometry composed of position and color vertices can be built.

struct MyPoint2D {
    float x;
    float y;
    float r;
    float g;
    float b;
    float a;
    void set(float x_, float y_, float r_, float g_, float b_, float a_) {
        x = x_;
        y = y_;
        r = r_;
        g = g_;
        b = b_;
        a = a_;
    }
};
QSGGeometry::Attribute MyPoint2D_Attributes[] = {
    QSGGeometry::Attribute::create(0, 2, GL_FLOAT, true),
    QSGGeometry::Attribute::create(1, 4, GL_FLOAT, false)
};
QSGGeometry::AttributeSet MyPoint2D_AttributeSet = {
    2,
    sizeof(MyPoint2D),
    MyPoint2D_Attributes
};
...
geometry = new QSGGeometry(MyPoint2D_AttributeSet, 2);
geometry->setDrawingMode(GL_LINES);
MyPoint2D *vertices = static_cast<MyPoint2D *>(geometry->vertexData());
vertices[0].set(0, 0, 1, 0, 0, 1);
vertices[1].set(width(), height(), 0, 0, 1, 1);
											

QSGGeometry is a software buffer and client-side in terms of OpenGL rendering, as the buffers used in 2D graphics typically consist of many small buffers that change every frame and do not benefit from being uploaded to graphics memory. However, the QSGGeometry supports hinting to the renderer that a buffer should be uploaded using the setVertexDataPattern() and setIndexDataPattern() functions. Whether this hint is respected or not is implementation specific.

注意

All classes with QSG prefix should be used solely on the scene graph’s rendering thread. See 场景图形和渲染 了解更多信息。

另请参阅

QSGGeometryNode 场景图形 - 自定义几何图形

class QSGGeometry ( attribs , vertexCount [ , indexCount=0 [ , indexType=UnsignedShortType ] ] ) ¶

param attribs

AttributeSet

param vertexCount

int

param indexCount

int

param indexType

int

Constructs a geometry object based on attributes .

The object allocate space for vertexCount vertices based on the accumulated size in attributes 和对于 indexCount .

indexType maps to the OpenGL index type and can be GL_UNSIGNED_SHORT and GL_UNSIGNED_BYTE . On OpenGL implementations that support it, such as desktop OpenGL, GL_UNSIGNED_INT can also be used.

Geometry objects are constructed with GL_TRIANGLE_STRIP as default drawing mode.

The attribute structure is assumed to be POD and the geometry object assumes this will not go away. There is no memory management involved.

PySide2.QtQuick.QSGGeometry. AttributeType ¶

This enum identifies several attribute types.

常量	描述
QSGGeometry.UnknownAttribute	Don’t care
QSGGeometry.PositionAttribute	Position
QSGGeometry.ColorAttribute	Color
QSGGeometry.TexCoordAttribute	Texture coordinate
QSGGeometry.TexCoord1Attribute	Texture coordinate 1
QSGGeometry.TexCoord2Attribute	Texture coordinate 2

PySide2.QtQuick.QSGGeometry. DataPattern ¶

The enum is used to specify the use pattern for the vertex and index data in a geometry object.

常量	描述
QSGGeometry.AlwaysUploadPattern	The data is always uploaded. This means that the user does not need to explicitly mark index and vertex data as dirty after changing it. This is the default.
QSGGeometry.DynamicPattern	The data is modified repeatedly and drawn many times. This is a hint that may provide better performance. When set the user must make sure to mark the data as dirty after changing it.
QSGGeometry.StaticPattern	The data is modified once and drawn many times. This is a hint that may provide better performance. When set the user must make sure to mark the data as dirty after changing it.
QSGGeometry.StreamPattern	The data is modified for almost every time it is drawn. This is a hint that may provide better performance. When set, the user must make sure to mark the data as dirty after changing it.

PySide2.QtQuick.QSGGeometry. DrawingMode ¶

The values correspond to OpenGL enum values like GL_POINTS , GL_LINES ，等。 QSGGeometry provies its own type in order to be able to provide the same API with non-OpenGL backends as well.

常量	描述
QSGGeometry.DrawPoints
QSGGeometry.DrawLines
QSGGeometry.DrawLineLoop
QSGGeometry.DrawLineStrip
QSGGeometry.DrawTriangles
QSGGeometry.DrawTriangleStrip
QSGGeometry.DrawTriangleFan

PySide2.QtQuick.QSGGeometry. Type ¶

The values correspond to OpenGL type constants like GL_BYTE , GL_UNSIGNED_BYTE ，等。 QSGGeometry provies its own type in order to be able to provide the same API with non-OpenGL backends as well.

常量	描述
QSGGeometry.ByteType
QSGGeometry.UnsignedByteType
QSGGeometry.ShortType
QSGGeometry.UnsignedShortType
QSGGeometry.IntType
QSGGeometry.UnsignedIntType
QSGGeometry.FloatType
QSGGeometry.Bytes2Type	Added in Qt 5.14.
QSGGeometry.Bytes3Type	Added in Qt 5.14.
QSGGeometry.Bytes4Type	Added in Qt 5.14.
QSGGeometry.DoubleType	Added in Qt 5.14.

PySide2.QtQuick.QSGGeometry. allocate ( vertexCount [ , indexCount=0 ] ) ¶

参数

• vertexCount – int

• indexCount – int

Resizes the vertex and index data of this geometry object to fit vertexCount vertices and indexCount indices.

Vertex and index data will be invalidated after this call and the caller must mark the associated geometry node as dirty, by calling node->markDirty( DirtyGeometry ) to ensure that the renderer has a chance to update internal buffers.

PySide2.QtQuick.QSGGeometry. attributeCount ( ) ¶

返回类型

int

Returns the number of attributes in the attrbute set used by this geometry.

PySide2.QtQuick.QSGGeometry. attributes ( ) ¶

返回类型

属性

Returns an array with the attributes of this geometry. The size of the array is given with attributeCount() .

static PySide2.QtQuick.QSGGeometry. defaultAttributes_ColoredPoint2D ( ) ¶

返回类型

AttributeSet

Convenience function which returns attributes to be used for per vertex colored 2D drawing.

static PySide2.QtQuick.QSGGeometry. defaultAttributes_Point2D ( ) ¶

返回类型

AttributeSet

Convenience function which returns attributes to be used for 2D solid color drawing.

static PySide2.QtQuick.QSGGeometry. defaultAttributes_TexturedPoint2D ( ) ¶

返回类型

AttributeSet

Convenience function which returns attributes to be used for textured 2D drawing.

PySide2.QtQuick.QSGGeometry. drawingMode ( ) ¶

返回类型

long

Returns the drawing mode of this geometry.

默认值为 GL_TRIANGLE_STRIP .

另请参阅

setDrawingMode()

PySide2.QtQuick.QSGGeometry. indexCount ( ) ¶

返回类型

int

Returns the number of indices in this geometry object.

PySide2.QtQuick.QSGGeometry. indexData ( ) ¶

返回类型

void

Returns a pointer to the raw index data of this geometry object.

另请参阅

indexDataAsUShort() indexDataAsUInt()

PySide2.QtQuick.QSGGeometry. indexDataAsUInt ( ) ¶

返回类型

uint

Convenience function to access the index data as an immutable array of 32-bit unsigned integers.

PySide2.QtQuick.QSGGeometry. indexDataAsUShort ( ) ¶

返回类型

quint16

Convenience function to access the index data as an immutable array of 16-bit unsigned integers.

PySide2.QtQuick.QSGGeometry. indexDataPattern ( ) ¶

返回类型

DataPattern

Returns the usage pattern for indices in this geometry. The default pattern is AlwaysUploadPattern .

另请参阅

setIndexDataPattern()

PySide2.QtQuick.QSGGeometry. indexType ( ) ¶

返回类型

int

Returns the primitive type used for indices in this geometry object.

PySide2.QtQuick.QSGGeometry. lineWidth ( ) ¶

返回类型

float

Gets the current line or point width or to be used for this geometry. This property only applies to line width when the drawingMode is DrawLines , DarwLineStrip, or DrawLineLoop . For desktop OpenGL, it also applies to point size when the drawingMode is DrawPoints .

默认值为 1.0

注意

When not using OpenGL, support for point and line drawing may be limited. For example, some APIs do not support point sprites and so setting a size other than 1 is not possible. Some backends may be able implement support via geometry shaders, but this is not guaranteed to be always available.

另请参阅

setLineWidth() drawingMode()

PySide2.QtQuick.QSGGeometry. markIndexDataDirty ( ) ¶

Mark that the vertices in this geometry has changed and must be uploaded again.

This function only has an effect when the usage pattern for vertices is StaticData and the renderer that renders this geometry uploads the geometry into Vertex Buffer Objects (VBOs).

PySide2.QtQuick.QSGGeometry. markVertexDataDirty ( ) ¶

Mark that the vertices in this geometry has changed and must be uploaded again.

This function only has an effect when the usage pattern for vertices is StaticData and the renderer that renders this geometry uploads the geometry into Vertex Buffer Objects (VBOs).

PySide2.QtQuick.QSGGeometry. setDrawingMode ( mode ) ¶

参数

mode – long

设置 mode to be used for drawing this geometry.

默认值为 DrawTriangleStrip .

另请参阅

drawingMode() DrawingMode

PySide2.QtQuick.QSGGeometry. setIndexDataPattern ( p ) ¶

参数

p – DataPattern

Sets the usage pattern for indices to p .

默认为 AlwaysUploadPattern . When set to anything other than the default, the user must call markIndexDataDirty() after changing the index data, in addition to calling markDirty() with DirtyGeometry .

另请参阅

indexDataPattern()

PySide2.QtQuick.QSGGeometry. setLineWidth ( w ) ¶

参数

w – float

Sets the line or point width to be used for this geometry to width . This property only applies to line width when the drawingMode is DrawLines , DrawLineStrip ，或 DrawLineLoop . For Desktop OpenGL, it also applies to point size when the drawingMode is DrawPoints .

注意

How line width and point size are treated is implementation dependent: The application should not rely on these, but rather create triangles or similar to draw areas. On OpenGL ES, line width support is limited and point size is unsupported.

另请参阅

lineWidth() drawingMode()

PySide2.QtQuick.QSGGeometry. setVertexDataPattern ( p ) ¶

参数

p – DataPattern

Sets the usage pattern for vertices to p .

默认为 AlwaysUploadPattern . When set to anything other than the default, the user must call markVertexDataDirty() after changing the vertex data, in addition to calling markDirty() with DirtyGeometry .

另请参阅

vertexDataPattern()

PySide2.QtQuick.QSGGeometry. sizeOfIndex ( ) ¶

返回类型

int

Returns the byte size of the index type.

This value is either 1 when index type is GL_UNSIGNED_BYTE or 2 when index type is GL_UNSIGNED_SHORT . For Desktop OpenGL, GL_UNSIGNED_INT 采用值 4 is also supported.

PySide2.QtQuick.QSGGeometry. sizeOfVertex ( ) ¶

返回类型

int

Returns the size in bytes of one vertex.

This value comes from the attributes.

static PySide2.QtQuick.QSGGeometry. updateColoredRectGeometry ( g , rect ) ¶

参数

• g – QSGGeometry

• rect – QRectF

Updates the geometry g with the coordinates in rect .

The function assumes the geometry object contains a single triangle strip of ColoredPoint2D vertices

static PySide2.QtQuick.QSGGeometry. updateRectGeometry ( g , rect ) ¶

参数

• g – QSGGeometry

• rect – QRectF

Updates the geometry g with the coordinates in rect .

The function assumes the geometry object contains a single triangle strip of Point2D vertices

static PySide2.QtQuick.QSGGeometry. updateTexturedRectGeometry ( g , rect , sourceRect ) ¶

参数

• g – QSGGeometry

• rect – QRectF

• sourceRect – QRectF

Updates the geometry g with the coordinates in rect and texture coordinates from textureRect .

textureRect should be in normalized coordinates.

g is assumed to be a triangle strip of four vertices of type TexturedPoint2D .

PySide2.QtQuick.QSGGeometry. vertexCount ( ) ¶

返回类型

int

Returns the number of vertices in this geometry object.

PySide2.QtQuick.QSGGeometry. vertexData ( ) ¶

返回类型

void

Returns a pointer to the raw vertex data of this geometry object.

另请参阅

vertexDataAsPoint2D() vertexDataAsTexturedPoint2D()

PySide2.QtQuick.QSGGeometry. vertexDataAsColoredPoint2D ( ) ¶

返回类型

ColoredPoint2D

Convenience function to access the vertex data as an immutable array of ColoredPoint2D .

PySide2.QtQuick.QSGGeometry. vertexDataAsPoint2D ( ) ¶

返回类型

Point2D

Convenience function to access the vertex data as an immutable array of Point2D .

PySide2.QtQuick.QSGGeometry. vertexDataAsTexturedPoint2D ( ) ¶

返回类型

TexturedPoint2D

Convenience function to access the vertex data as an immutable array of TexturedPoint2D .

PySide2.QtQuick.QSGGeometry. vertexDataPattern ( ) ¶

返回类型

DataPattern

Returns the usage pattern for vertices in this geometry. The default pattern is AlwaysUploadPattern .

另请参阅

setVertexDataPattern()