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我正在用 GTK2/3 + OpenGL 编写一个程序,我运行了该程序的两个版本:
- (a) GTK+2 + GtkGlext 扩展 -> 效果很好!
- (b) GTK+3 + LibX11 -> 工作得很好!
一切看起来都很好,除了 (a) 中的渲染速度明显快于 (b) 中的渲染速度……我不知道为什么。
以下是用于创建 OpenGL 上下文的代码部分的一些示例:
-
(a)
// To create the context, and the associated GtkWidget
GdkGLConfig * glconfig = gdk_gl_config_new_by_mode (GDK_GL_MODE_RGBA | GDK_GL_MODE_DEPTH | GDK_GL_MODE_DOUBLE);
GtkWidget * drawing_area = gtk_drawing_area_new ();
gtk_widget_set_gl_capability (drawing_area, glconfig, NULL, TRUE, GDK_GL_RGBA_TYPE);
g_signal_connect (G_OBJECT (drawing_area), "expose-event", G_CALLBACK (on_expose), data);
// And later on to draw using the OpenGL context:
gboolean on_expose (GtkWidget * widg, GdkEvent * event, gpointer data)
{
GdkGLContext * glcontext = gtk_widget_get_gl_context (widg);
GdkGLDrawable * gldrawable = gtk_widget_get_gl_drawable (widg);
if (gdk_gl_drawable_gl_begin (gldrawable, glcontext))
{
// OpenGL instructions to draw here !
gdk_gl_drawable_swap_buffers (view -> gldrawable);
gdk_gl_drawable_gl_end (view -> gldrawable);
}
return TRUE;
}
-
(b)
// To create the GtkWidget
GtkWidget * drawing_area = gtk_drawing_area_new ();
// Next line is required to avoid background flickering
gtk_widget_set_double_buffered (drawing_area, FALSE);
g_signal_connect (G_OBJECT (drawing_area), "realize", G_CALLBACK(on_realize), data);
g_signal_connect (G_OBJECT (drawing_area), "draw", G_CALLBACK(on_expose), data);
// To create the OpenGL context
GLXContext glcontext;
G_MODULE_EXPORT void on_realize (GtkWidget * widg, gpointer data)
{
GdkWindow * xwin = gtk_widget_get_window (widg);
GLint attr_list[] = {GLX_DOUBLEBUFFER,
GLX_RGBA,
GLX_DEPTH_SIZE, 16,
GLX_RED_SIZE, 8,
GLX_GREEN_SIZE, 8,
GLX_BLUE_SIZE, 8,
None};
XVisualInfo * visualinfo = glXChooseVisual (GDK_WINDOW_XDISPLAY (xwin), gdk_screen_get_number (gdk_window_get_screen (xwin)), attr_list);
glcontext = glXCreateContext (GDK_WINDOW_XDISPLAY (xwin), visualinfo, NULL, TRUE);
xfree (visualinfo);
}
// To Draw using the OpenGL context
G_MODULE_EXPORT gboolean on_expose (GtkWidget * widg, cairo_t * cr, gpointer data)
{
GdkWindow * win = gtk_widget_get_window (widg);
if (glXMakeCurrent (GDK_WINDOW_XDISPLAY (xwin), GDK_WINDOW_XID (xwin), glcontext))
{
// OpenGL instructions to draw here !
glXSwapBuffers (GDK_WINDOW_XDISPLAY (win), GDK_WINDOW_XID (win));
}
return TRUE;
}
为了理解为什么(a)比(b)更快,我下载了 GtkGLext 库的源代码,阅读它们,发现命令与调用 X11 完全相同。
现在我的想法是(b)中的以下行
gtk_widget_set_double_buffered (drawing_area, FALSE);
搞乱了渲染,然后我就无能为力了......
或者 OpenGL 上下文之间存在差异,这可能可以解释我注意到的行为,如果我朝这个方向跟进,我需要尽可能多地比较两个上下文......到目前为止,我选择了似乎是获取一些信息的最常用方法:
OpenGL Version : 3.0 Mesa 12.0.3
OpenGL Vendor : nouveau
OpenGL Renderer : Gallium 0.4 on NVCF
OpenGL Shading Version : 1.30
Color Bits (R,G,B,A) : 8, 8, 8, 0
Depth Bits : 24
Stencil Bits : 0
Max. Lights Allowed : 8
Max. Texture Size : 16384
Max. Clipping Planes : 8
Max. Modelview Matrix Stacks : 32
Max. Projection Matrix Stacks : 32
Max. Attribute Stacks : 16
Max. Texture Stacks : 10
Total number of OpenGL Extensions : 227
Extensions list:
N°1 : GL_AMD_conservative_depth
N°2 : GL_AMD_draw_buffers_blend
...
但两种上下文都返回完全相同的信息......
感谢您已经到达那里......现在我的问题是:
有没有办法输出尽可能多的有关 OpenGL 上下文的信息,以及如何输出?
我欢迎对我正在做的事情提出任何其他建议!
S.
PS:我正在研究使用 GTK3 的 GtkGLArea 小部件,但如上所述here我还没到那儿。
[编辑] 一些 OpenGL 指令:
// OpenGL instructions to draw here !
glLoadIdentity ();
glPushMatrix ();
// d is the depth ... calculated somewhere else
glTranslated (0.0, 0.0, -d);
// Skipping the rotation part for clarity, I am using a quaternion
rotate_camera ();
// r, g, b and a are GLFloat values
glClearColor (r,g,b,a);
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glDisable (GL_LIGHTING);
int i;
// nbds is the number of chemical bonds
GLfloat * lineVertices;
// This is "roughly" what I do to draw chemical bonds, to give you an idea
for (i=0; i<nbds;i++)
{
// get_bonds (i) gives backs a 6 float array
lineVertices = get_bonds(i);
glPushMatrix();
glLineWidth (1.0);
glEnableClientState (GL_VERTEX_ARRAY);
glVertexPointer (3, GL_FLOAT, 0, lineVertices);
glDrawArrays (GL_LINES, 0, 2);
glDisableClientState (GL_VERTEX_ARRAY);
glPopMatrix();
}
glEnable (GL_LIGHTING);
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