1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCanvas3D module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
** * Neither the name of The Qt Company Ltd nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example textureandlight
\since QtCanvas3D 1.0
\title Lit and Textured Cube Example
\ingroup qtcanvas3d-examples
\brief A simple cube with texturing and lighting.
The Lit and Textured Cube example goes through the basics of using
Qt Canvas 3D.
\image textureandlight-example.png
\section1 Qt Quick Implementation
\section2 Creating Canvas3D
In \l{textureandlight/qml/textureandlight/main.qml}{main.qml}, we add a
Canvas3D under the root \c Item:
\snippet textureandlight/qml/textureandlight/main.qml 0
\dots
Inside it, we catch the \c initializeGL and \c paintGL signals to forward the
initialization and rendering calls to the js object:
\snippet textureandlight/qml/textureandlight/main.qml 1
\section2 Importing the JavaScript File
We import the JavaScript file in the QML:
\snippet textureandlight/qml/textureandlight/main.qml 4
In the \c initializeGL function of the JavaScript, we initialize the OpenGL
state. We also create the TextureImage and register handlers for image
load success and fail signals. If the load succeeds, the OpenGL texture
is created and filled with pixel data from the loaded image.
\section1 JavaScript Implementation
\section2 Matrix Library
In \l {textureandlight/qml/textureandlight/textureandlight.js}
{textureandlight.js}, we first include a fast matrix library. Using this
makes it a lot easier to handle 3D math operations such as matrix
transformations:
\snippet textureandlight/qml/textureandlight/textureandlight.js 0
\section2 initializeGL Function
Let's take a closer look at the \c initializeGL function. It is called by
Canvas3D once the render node is ready.
First of all, we need to get a Context3D from our Canvas3D. We want
a context that supports depth buffer and antialising:
\snippet textureandlight/qml/textureandlight/textureandlight.js 1
Then we initialize the OpenGL state for the context:
\snippet textureandlight/qml/textureandlight/textureandlight.js 2
Next, let's take a look into shader initialization in the
\c initShaders function, which we call in \c{initializeGL}. First we define
the vertex shader:
\snippet textureandlight/qml/textureandlight/textureandlight.js 3
We follow that up by defining a fragment shader:
\snippet textureandlight/qml/textureandlight/textureandlight.js 4
Then we need to create the shader program (Canvas3DProgram), attach the shaders
to it, and then link and use the program:
\snippet textureandlight/qml/textureandlight/textureandlight.js 5
And finally, look up and store the vertex attributes and uniform locations:
\snippet textureandlight/qml/textureandlight/textureandlight.js 6
After initializing the shader program, we set up the vertex buffer in
\c initBuffers function. Let's look at the vertex index buffer creation
as an example:
\snippet textureandlight/qml/textureandlight/textureandlight.js 7
Above, first we create the buffer, then bind it and finally insert the
data into it. Other buffers are all handled in a similar fashion.
As the final step in \c{initializeGL}, we create a texture image from
TextureImageFactory, and register handlers for \c imageLoaded and
\c imageLoadingFailed signals. Once the texture image is successfully
loaded, we create the actual texture:
\snippet textureandlight/qml/textureandlight/textureandlight.js 8
\section2 paintGL Function
\c paintGL is called by Canvas3D whenever it is ready to receive a new
frame. Let's go through the steps that are done in each render cycle.
First we check if canvas has been resized or if pixel ratio has changed,
and update the projection matrix if necessary:
\snippet textureandlight/qml/textureandlight/textureandlight.js 9
Then we clear the render area using the clear color set in \c{initializeGL}:
\snippet textureandlight/qml/textureandlight/textureandlight.js 10
Next we reset the model view matrix and apply translation and rotations:
\snippet textureandlight/qml/textureandlight/textureandlight.js 11
As we have a lit cube, we invert and transpose the model view matrix to
be used for lighting calculations:
\snippet textureandlight/qml/textureandlight/textureandlight.js 12
And finally we draw the cube:
\snippet textureandlight/qml/textureandlight/textureandlight.js 13
\section1 Logging
Qt Canvas 3D uses Qt's categorized logging feature. This example enables
all Qt Canvas 3D log output with the code shown below. For more on
Canvas3D's logging features refer to \l {Qt Canvas 3D Logging}.
\snippet textureandlight/main.cpp 0
*/
|
