Automotive User Interfaces and Interactive Vehicular Applications

5.1 Seamlessly Integrated Design Workflow
Professional modeling tools are used to create design drafts which
are then imported into dedicated HMI-development tools using
widespread standardized exchange formats. The data exchange
formats in question are those supported by state-of-the-art design
tools, e.g. image formats such as JPG, PNG, TGA, PSD, etc. and
3D design formats such as FBX and COLLADA. The data to be
exchanged includes graphical artifacts (3D-models, textures,
graphics), structural information about local or spatial relation
between elements as well as chronological sequences in form of
animations. 3D models also include special, non-visible elements
like cameras and light sources.
After the design drafts have been imported they are available for
usage and further adaption in the HMI development tools. These
tools preserve and visualize all previously defined relations
between the contained artifacts, such as the spatial relation of the
scene-graph and animation sequences. The HMI development tool
manages all imported design drafts in a library, thus containing
elements that originate from different sources. These elements can
be used to compose complex screen designs. This allows, for
example, embedding a 3D vehicle-model coming from the CADdepartment
into design elements of a different source, such as a
background image. This approach allows building consistent
HMIs which are made of various graphical elements in a modular
way. The individual modules can be of different complexity,
ranging from atomic models or images up to complete screens and
sceneries. The same modules can be reused for creating multiple
views or scenes. They can also be used to create different design
variants. By importing graphical design artifacts, animation
sequences, and their relation redundant efforts can be omitted
because neither elements nor their relations need to be specified in
detail or created again.
Extensive rendering techniques like ray-tracing or radiosity are
used in PC environments for 3D designs. On the one hand such
rendering techniques provide realistic and sophisticated graphics.
On the other hand though, they require computing power and
architectures that are not available on embedded systems, while at
the same time consume render time which does not allow realtime
rendering. Rendering a single screen on a PC can take up to
several minutes, depending on the complexity of the screen and
effects. For 3D GUIs in vehicles, the same screen is required to be
rendered in real-time, approximately 20 to 60 times a second,
while maintaining a good appearance. For this reason, different
rendering techniques are required to use 3D GUIs on embedded
systems. This, in turn, can lead to a different appearance, which
needs to be corrected by manual adjustments. Examples are
inappropriate gap dimensions, aliasing effects, or different
approaches for implementation of visual effects.
To overcome this discrepancy between traditional design and high
render performance on target systems, HMI-development tools
allow for adaptation and adjustment of graphical artifacts in
different stages. While adaptation of 3D models is usually
performed in 3D modeling tools, 3D HMI-development tools
support adaptation depending on the rendering techniques and
capabilities of the target system. Examples of the latter are the
development of shader-programs for OpenGL-based rendering or
the partitioning of a screen into multiple hardware layers. If
necessary, the scene-graph can also be optimized with respect to
light sources, camera settings, and model-relations. Furthermore,
imported animations can be applied or enriched and new
animations can be created.
These examples show that seamlessly integrated toolchains call
for new activities and also affect the creation of the original
design drafts. Furthermore, a new role needs to be introduced in
the development process, a so called “Technical Artist”. Its task is
to perform the optimizations for each particular target system.
This requires knowledge of the capabilities of this environment
and an understanding of visual design aspects at the same time.
The role can be taken on by either an artist with technical skills or
a software developer with graphical understanding.
Seamless model integration enables efficient development process
for graphical design by omitting the need for extensive, detailed
and potentially mistakable specifications. Iteration can be
performed easier and faster since the barrier of media disruption
and its related efforts is no longer present. It allows major
adjustments and changes to the graphical design even in late
development phases.
Seamless model integration also leads to an involvement of visual
designers in the HMI development process on a technical level.
This, however, poses new challenges. Up to now the concrete
implementation of a design draft (e.g. polygon-count of 3D
models or usage of light sources) had no impact to the final
software for the target system due to process-separation per
specification. This is not the case in seamlessly integrated
development processes. Thus, the design drafts must take target
specific specialties and requirements into account. This includes
optimizing texture-sizes and 3D models with respect to rendering
performance, placing light sources carefully, and implementing
effects in a technology-aware way. Furthermore, the structure of
the scene-graph needs to satisfy functional HMI requirements.
This leads to unusual requirements for design departments: They
cannot chose an effect for the sole reason that it leads to the right
graphical appearance. Instead of that, it has to be done with
respect to the requirements and constraints of the final system. For
instance, instead of using path-extrusion features of the modeling
tool it may be necessary to model a fully extruded object which is
reduced by shader-programs at run-time to achieve the same
graphical appearance. Another example is the functional modeling
of a vehicle miniature showing which doors are currently opened.
For a proof-of-concept it is sufficient to only functionally model
one door. However, the models required for creating the final
HMI need to allow moving all doors in a physically accurate way.
As mentioned before, such tasks are carried out by ”Technical
Artists” who ideally perform them based on the original models of
the design drafts. After that, the modified models are re-imported
into the HMI-development tools. Because optimizations and
adaptations are usually performed iteratively the HMIdevelopment
tools need to support updating already imported
artifacts after they have been modified externally while preserving
the adoptions performed in the HMI-development tool. Integration
of behavior models and their loose coupling with graphical
elements allows setting up a modular and flexible tool-supported
process chain.
The HMI models need to be transformed into a format suitable for
execution in the target system or a simulation of the target
environment on a host system. HMI development tools need to
make this task as easy as possible to enable rapid evaluation of
design drafts in realistic settings. This in turn shortens the
development time and provides higher flexibility with respect to
design adaptations and prototype development.
5.2 Seamlessly Integrated Behavior Modeling
According to the model-view-controller pattern the specification
and implementation of the HMI-behavior is the second major