class QSGGeometry#

The QSGGeometry class provides low-level storage for graphics primitives in the Qt Quick Scene Graph . More…

Synopsis#

Methods#

Static functions#

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description#

The 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, also called primitive topology, is specified with setDrawingMode() .

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.

The 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, FloatType, true),
    QSGGeometry::Attribute::create(1, 4, FloatType, false)
};

QSGGeometry::AttributeSet MyPoint2D_AttributeSet = {
    2,
    sizeof(MyPoint2D),
    MyPoint2D_Attributes
};

...

geometry = new QSGGeometry(MyPoint2D_AttributeSet, 2);
geometry->setDrawingMode(DrawLines);

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);

The QSGGeometry is a software buffer and client-side in terms of accelerated 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.

Note

All classes with QSG prefix should be used solely on the scene graph’s rendering thread. See Scene Graph and Rendering for more information.

See also

QSGGeometryNode Scene Graph - Custom Geometry

class AttributeType#

This enum identifies several attribute types.

Constant

Description

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
class DataPattern#

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

Constant

Description

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.
class DrawingMode#

(inherits enum.IntEnum) Specifies the drawing mode, also called primitive topology.

Note

Starting with Qt 6 the scene graph only exposes topologies that are supported across all the supported 3D graphics APIs. As a result, the values DrawLineLoop and DrawTriangleFan are no longer supported at run time in Qt 6, even though the enum values themselves are still present.

Constant

Description

QSGGeometry.DrawPoints

QSGGeometry.DrawLines

QSGGeometry.DrawLineStrip

QSGGeometry.DrawTriangles

QSGGeometry.DrawTriangleStrip
class Type#

Specifies the component type in the vertex data.

Constant

Description

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.
__init__(attribs, vertexCount[, indexCount=0[, indexType=QSGGeometry.Type.UnsignedShortType]])#
Parameters:

  • attribs – AttributeSet

  • vertexCount – int

  • indexCount – int

  • indexType – int

Constructs a geometry object based on attributes.

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

The indexType can be UnsignedShortType or UnsignedIntType. Support for the latter depends on the graphics API implementation used at run time, and may not always be available.

Geometry objects are constructed by default with DrawTriangleStrip as the drawing mode.

Note

attributes and the Attribute objects referenced by it must stay valid for the entire lifetime of the QSGGeometry . QSGGeometry stores a reference to attributes and does not delete the Attribute objects.

allocate(vertexCount[, indexCount=0])#
Parameters:

  • 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.

attributeCount()#
Return type:

int

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

attributes()#
Return type:

Attribute

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

static defaultAttributes_ColoredPoint2D()#
Return type:

AttributeSet

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

static defaultAttributes_Point2D()#
Return type:

AttributeSet

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

static defaultAttributes_TexturedPoint2D()#
Return type:

AttributeSet

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

drawingMode()#
Return type:

int

Returns the drawing mode of this geometry.

The default value is DrawTriangleStrip .

See also

setDrawingMode()

indexCount()#
Return type:

int

Returns the number of indices in this geometry object.

indexData()#
Return type:

void

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

indexDataAsUInt()#
Return type:

uint

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

indexDataAsUShort()#
Return type:

quint16

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

indexDataPattern()#
Return type:

DataPattern

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

indexType()#
Return type:

int

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

lineWidth()#
Return type:

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 or DrawLineStrip . When supported, it also applies to point size when the drawingMode is DrawPoints .

The default value is 1.0

Note

Support for point and line drawing may be limited at run time, depending on the platform and graphics API. For example, some APIs do not support point sprites and so setting a size other than 1 is not possible.

Note

The width of 1.0 is always supported.

See also

setLineWidth() drawingMode()

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).

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).

setDrawingMode(mode)#
Parameters:

mode – int

Sets the mode to be used for drawing this geometry.

The default value is DrawTriangleStrip .

setIndexDataPattern(p)#
Parameters:

p – DataPattern

Sets the usage pattern for indices to p.

The default is 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 .

setLineWidth(w)#
Parameters:

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 or DrawLineStrip . When supported, it also applies to point size when the drawingMode is DrawPoints .

Note

Support for point and line drawing may be limited at run time, depending on the platform and graphics API. For example, some APIs do not support point sprites and so setting a size other than 1 is not possible.

Note

The width of 1.0 is always supported.

See also

lineWidth() drawingMode()

setVertexDataAsPoint2D(points)#
Parameters:

points – .list of QSGGeometry.Point2D

Sets the vertex data from a list of QSGGeometry.Point2D. The list size must match the allocated number of vertexes as returned by QSGGeometry.vertexCount().

setVertexDataPattern(p)#
Parameters:

p – DataPattern

Sets the usage pattern for vertices to p.

The default is 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 .

sizeOfIndex()#
Return type:

int

Returns the byte size of the index type.

This value is either 2 when the index type is UnsignedShortType , or 4 when the index type is UnsignedIntType .

sizeOfVertex()#
Return type:

int

Returns the size in bytes of one vertex.

This value comes from the attributes.

static updateColoredRectGeometry(g, rect)#
Parameters:

Updates the geometry g with the coordinates in rect.

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

static updateRectGeometry(g, rect)#
Parameters:

Updates the geometry g with the coordinates in rect.

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

static updateTexturedRectGeometry(g, rect, sourceRect)#
Parameters:

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 .

vertexCount()#
Return type:

int

Returns the number of vertices in this geometry object.

vertexData()#
Return type:

void

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

vertexDataAsColoredPoint2D()#
Return type:

ColoredPoint2D

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

vertexDataAsPoint2D()#
Return type:

PyObject*

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

vertexDataAsTexturedPoint2D()#
Return type:

TexturedPoint2D

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

vertexDataPattern()#
Return type:

DataPattern

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