During integration of lighting simulation systems into CATIA CAD often are needed additional view modes initially absent in this CAD. This article describes adding such view modes directly in CATIA workspace window using CATIA's native CAA RADE programming environment. Adding these new view modes can significantly simplify user's preparation of data for lighting simulation. Here the following additional view modes are mentioned: geometry tessellation to triangular meshes (in the wireframe mode), heat map display of the optical values distribution over the scene, and spherical panorama preview. In the paper the problems which may occur while trying to redraw the additional data in real time are described and possible ways of solving or bypassing them are proposed. Using the new display modes provides a possibility of tuning some scene parameters and viewing preliminary results immediately while rendering of such scenes may take several hours. Such additional functionality can significantly increase the modeling process.
Optical simulation systems allow synthesizing photorealistic images of various virtual
3D scenes as well as obtaining numerical values of various optical parameters of
virtual objects, with sufficient speed and accuracy [
CATIA system is one of the most popular CAD systems, especially in automobile
and aviation industry, and physical accuracy of the modeling results are especially
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important for CATIA users [
At the initial stage of the integration of optical simulation systems with existing
CAD it is sufficient to develop an algorithm of data conversion from the internal data
format of the CAD to some format suitable for processing in the optical simulation
system. However, the most convenient for end-users way of integration is direct
integration of the user interface controls of this system in the native user interface of the
target CAD. It allows user to consider the combined complex of the initial CAD
system and optical simulation system integrated into it as a monolith program [
CATIA Workspace is a document window where all scene objects are shown and
which provides possibility of their visual editing. As workspace requires real-time
update of the shown data during editing, usually it displays a scene with draft quality,
while some details with potentially long rendering time are omitted. The CATIA
CAD system provides different modes and additional possibilities for displaying
scene objects in its workspace. However, CATIA system is primarily intended for
geometric modeling of parts in the mechanical engineering. Creation of plug-ins for
CATIA intended for some other purposes, for example, for optical simulation tasks,
requires additional display modes which are not provided by the built-in functionality
of the CATIA system. In this work we describe insertion of such modes using the
CATIA’s own programming system – CAA RADE (integrated with Microsoft Visual
Studio development environment) [
Among the view modes absent in the CATIA CAD system but important for optical simulation tasks there are most often required displaying of tessellation of geometrical objects into triangular meshes with different subdivision accuracy, and also showing optical values at the surfaces of the geometrical objects in the form of a heat map. Also in this article is described a functionality of showing spherical panorama used as a background image directly in the CATIA workspace viewport. 3
Geometrical objects in CATIA usually represent themselves by analytically defined surfaces. For tasks of computational optics, in most cases such surfaces must be tessellated into triangular meshes. Size of the obtained triangles can be different for achievement of balance between calculation speed and accuracy. Tessellation proce
Elaboration of New Viewing Modes in CATIA CAD for Lighting Simulation Purpose 3
dure may often take very long time [
The CATIA system provides a possibility of creating special temporary geometric models which are shown in its workspace but are not inserted into the virtual scene and are not saved to files. For triangular mesh display we use such temporary objects. There is also possibility to set an 0wn viewing mode (wireframe, shaded etc.) for each object in CATIA system. So we always show tessellation results in wireframe mode in spite of the current global viewing mode for scene objects. It should be noticed that if objects in the workspace are painted in the wireframe mode and their coordinates coincide with coordinates of other objects painted in some other mode, then the first ones are not overlapped with the last ones. So there is no need in some additional manipulations with depth buffer to guarantee permanent visibility of triangle meshes in wireframe.
Viewport orientation parameters in CATIA have an influence not only to the scene objects, but to the temporary visualized objects too. So there are not needed in any additional actions to provide correspondence between source object and its tessellation results during viewport transformations. But still the tessellation results may do not correspond to the initial object if this object has been changed since the last tessellation procedure. Currently we have decided not to add any automatic rebuilding of the tessellation data because this process may take significant time. So it will embarrass user’s editing of the scene objects.
The CATIA viewport with tessellated mesh for two different tessellation sag values is shown on Fig. 1. Tessellation parameters at the upper part of the image are insufficient, so tessellation sag has been reduced and the result is shown at the lower part of the figure. 4
The so-called heat map mode means graphical representation of the function of
several variables. Value of the displayed quantity is expressed with color of the
corresponding pixel [
CATIA system does not have built-in functionality for displaying heat maps. We had to develop such functionality from scratch by extending the existing display modes. It had been decided to create a special texture for scene objects and use Shading with Material for displaying it. Shading with Material mode allows displaying scene and temporary objects with applied textures directly in the workspace.
We have developed the special method which significantly simplified applying the
heat map to the meshes in the viewport. For objects displayed in the workspace we
have selected the one-dimensional texture coordinates mode. Then we created a
texture with single-pixel width which represents smooth color gradient corresponding to
the colors of the heat map. Value of the single texture coordinates for each mesh
vertex is set equal to ration of the luminance (illuminance etc.) value in this vertex to the
difference between maximal and minimal luminance of the current scene. In such a
case each specific vertex is painted with the color corresponding to the required value
of the displayed quantity. Using linear interpolation for pixels located between
vertices with explicitly set luminance/illuminance value provides satisfactory quality of
shading for these pixels. The described texture is being generated automatically
depending on the current luminance/illuminance data and heat map parameters.
Applying the generated textures directly to the CATIA scene objects is hardly
possible. The tree of representations of CATIA scene objects can have complicated
structure which does not always correspond to tree structure of the scene objects
themselves. Besides this, it was already told that we use tessellation (conversion of initial
CATIA scene objects to triangle meshes according to specified parameters) so
calculated luminance/illuminance values significantly depend on these parameters because
tessellated meshes may have noticeable difference from initial scene objects. That is
why we display heat map upon the additionally created temporary geometrical meshes
similar to viewing tessellation results. There comes another problem – it is necessary
to display these newly created objects in front of the initial CATIA scene objects in
the viewport. Because we were unable to manipulate the depth buffer of the CATIA
main viewport, we have decided just to hide the initial geometry in the workspace. To
do so, we obtained pointer to the graphic representation (a CATRep object) [
As displaying any bitmap textures in the CATIA workspace viewport is possible only in the Shading with Material display mode, we disable turning on heat map mode in case if any other view mode is currently active. But user also can switch from Shading with Material view mode to other view mode already after heat map display had been turned on. For automatic turning off heat map display in this case, we had to set up the callback for the VIEWER_UPDATE event. This event is being activated each time after any redraw of the viewport. The event handler checks the current view mode and turns off heat map display if the mode is not Shading with Material.
CATIA workspace with heat map display turned on and dialog box containing controls of this mode is shown on Fig 2. The color bar shown at the left of the dialog box shown on Fig. 2 corresponds to the 1-dimensional texture applied to the surfaces. 5
Spherical panorama is an image combined from several photos which display a view from some point in all directions (360 x 180 degrees). Usage of a spherical panorama as a background image allows increasing realism of artificially created model. The model is being inserted in such panorama which is obtained from a photo taken with special equipment. Such panorama can also be a light source for the created models if it has high dynamic range [9].
For setting up correct orientation parameters of the spherical panorama relatively to the built models it is desirable to show the panorama preview directly in the CATIA viewport. User should have a possibility to change common parameters of the panorama and its orientation and see the results in real time.
For solving this task we created the temporary geometrical representation with spherical shape in CATIA viewport. The entire scene built by user should be inscribed into this sphere. The simplest way to place the sphere visually behind all other scene objects would be forced changing of the workspace depth buffer. But unfortunately, as in the previous cases, absence of direct access to the CATIA depth buffer functions for third-party programmers forced us to use some actions for bypassing this problem. So the sphere was created just as a usual temporary geometric representation in the workspace. The center and radius of the sphere are set automatically and are changed corresponding to viewpoint orientation change.
Initially the sphere center is set equal to the current camera position and sphere radius is set equal to some constant. Then, in the callback of the viewport redraw event, there is obtained current radius of the scene bounding sphere (which includes the radius of the newly created sphere object). If the obtained radius is more than in 1.00001 times larger than the radius of the panorama object, then the panorama radius is doubled. Such stepped radius change with additional threshold allows to avoid infinite looping which may appear because global bounding sphere radius obtained through CATIA API functions includes the newly created sphere radius too.
The preview of a spherical panorama together with a rough car model in the CATIA workspace is shown on Fig.3. User can change camera orientation in real time and see the preview immediately while high quality scene rendering may take several hours.
Elaboration of New Viewing Modes in CATIA CAD for Lighting Simulation Purpose 7
Implementation of additional viewing modes provided better integration of optical simulation and physically accurate rendering system into CATIA CAD and made the work of end user with the program complex more convenient. Lighting engineers who use extended CATIA program complex now are able to edit the required models dynamically. Added viewing modes allow them to view immediately the reflectance of these changes to the results of optical simulation as well as preview of the changes without repeating the time-consuming procedures of optical simulations after each adjustment of scene parameters.