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
184
185
186
187
188
189
190
191
192
193
194
195
|
// Copyright (C) 2020 Klaralvdalens Datakonsult AB (KDAB).
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\page qt3drender-porting-to-rhi.html
\title Qt 3D Render Porting to RHI
\brief This section details what's involved in porting Qt 3D materials to
work with RHI.
As a reminder, in Qt 6, Qt 3D will default to using it's RHI rendering
backend.
Using the older OpenGL backend from the Qt 5 series remains possible. This
can be enabled by setting environment variable QT3D_RENDERER to opengl.
This is required in case you don't want to port your application to support
RHI or in case you need features which are currently limited or not
available on the RHI backend.
Currently, the known RHI limitations are:
\list
\li No way to explicitly Blit (you have to blit manually by rendering a
quad into a framebuffer)
\li MemoryBarrier cannot be set explicitly
\li Not all Texture Formats are available
\li Draw Indirect is currently not supported
\li Geometry Shaders are currently not supported.
\li Different RHI backends might support different feature set.
\endlist
Please also take care not to confuse the Qt 3D OpenGL render backend with
Qt 3D's RHI render backend running on top of OpenGL.
RHI is an abstraction over different graphics API. This means that on a
given platform, several RHI could use several backends.
To force RHI to use a given backend, the QSG_RHI_BACKEND environment variable
should be set to one of opengl, vulkan, metal, directx.
\section1 Add RHI Compatible Techniques
To add RHI support to a Qt 3D Material / Effect, a new Technique targeting
RHI will be required. As of this writing, the only valid RHI version is 1.0.
\badcode
Material {
Effect {
techniques: [
Technique {
id: gl3Technique
graphicsApiFilter {
api: GraphicsApiFilter.OpenGL
profile: GraphicsApiFilter.CoreProfile
majorVersion: 3
minorVersion: 1
}
renderPasses: RenderPass {
id: gl3Pass
shaderProgram: ShaderProgram {
...
}
}
},
Technique {
id: rhiTechnique
graphicsApiFilter {
api: GraphicsApiFilter.RHI
profile: GraphicsApiFilter.NoProfile
majorVersion: 1
minorVersion: 0
}
renderPasses: RenderPass {
id: rhiPass
shaderProgram: ShaderProgram {
...
}
}
}
]
}
}
\endcode
\badcode
QMaterial *material = new QMaterial();
QEffect *effect = new QEffect();
// Set the effect on the material
material->setEffect(effect);
{
QTechnique *gl3Technique = new QTechnique();
QRenderPass *gl3Pass = new QRenderPass();
QShaderProgram *glShader = new QShaderProgram();
// Set the shader on the render pass
gl3Pass->setShaderProgram(glShader);
// Add the pass to the technique
gl3Technique->addRenderPass(gl3Pass);
// Set the targeted GL version for the technique
gl3Technique->graphicsApiFilter()->setApi(QGraphicsApiFilter::OpenGL);
gl3Technique->graphicsApiFilter()->setMajorVersion(3);
gl3Technique->graphicsApiFilter()->setMinorVersion(1);
gl3Technique->graphicsApiFilter()->setProfile(QGraphicsApiFilter::CoreProfile);
// Add the technique to the effect
effect->addTechnique(gl3Technique);
}
{
QTechnique *rhiTechnique = new QTechnique();
QRenderPass *rhiPass = new QRenderPass();
QShaderProgram *rhiShader = new QShaderProgram();
// Set the shader on the render pass
rhiPass->setShaderProgram(glShader);
// Add the pass to the technique
rhiTechnique->addRenderPass(rhiPass);
// Set the targeted RHI version for the technique
rhiTechnique->graphicsApiFilter()->setApi(QGraphicsApiFilter::RHI);
rhiTechnique->graphicsApiFilter()->setMajorVersion(1);
rhiTechnique->graphicsApiFilter()->setMinorVersion(0);
rhiTechnique->graphicsApiFilter()->setProfile(QGraphicsApiFilter::NoProfile);
// Add the technique to the effect
effect->addTechnique(rhiTechnique);
}
\endcode
\section1 Creating a RHI compatible shader
Regardless on which backend RHI will be running on top of, the shaders will
be written in GLSL 450.
Changes are minimal compared to earlier GLSL versions, the main noticeable
differences are in the way uniforms are declared.
Please also note that in and out variables need to have their locations defined
and that they should be consistent between shader stages.
\badcode
#version 450 core
layout(location = 0) in vec3 vertexPosition;
layout(location = 0) out vec3 worldPosition;
layout(std140, binding = 0) uniform qt3d_render_view_uniforms {
mat4 viewMatrix;
mat4 projectionMatrix;
mat4 uncorrectedProjectionMatrix;
mat4 clipCorrectionMatrix;
mat4 viewProjectionMatrix;
mat4 inverseViewMatrix;
mat4 inverseProjectionMatrix;
mat4 inverseViewProjectionMatrix;
mat4 viewportMatrix;
mat4 inverseViewportMatrix;
vec4 textureTransformMatrix;
vec3 eyePosition;
float aspectRatio;
float gamma;
float exposure;
float time;
float yUpInNDC;
float yUpInFBO;
};
layout(std140, binding = 1) uniform qt3d_command_uniforms {
mat4 modelMatrix;
mat4 inverseModelMatrix;
mat4 modelViewMatrix;
mat3 modelNormalMatrix;
mat4 inverseModelViewMatrix;
mat4 modelViewProjection;
mat4 inverseModelViewProjectionMatrix;
};
void main()
{
...
}
\endcode
For more details about shader changes, please checkout \l
{Qt3DRender::QShaderProgram}
\section1 Qt 3D Extras
Materials in Qt 3D Extras have been ported to RHI.
*/
|
