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Tema: Case Study Of Blender Real Time Engine on SR-686 Roosevelt Boulevard

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    Case Study Of Blender Real Time Engine on SR-686 Roosevelt Boulevard

    CASE STUDY: Of Blender’s Real Time Engine on SR-686 Roosevelt Boulevard
    by Brian Treacy


    Blender’s Real-Time Engine is not limited to just games. This article explains how I mixed Open-Source tools such as Blender and Gimp with proprietary tools such as MicroStation and Photoshop to produce a real-time walk-through of a proposed design of SR686 Roosevelt Boulevard for a presentation to Florida’s Department of Transportation. Roosevelt Boulevard is located in Tampa, Florida adjacent to the St. Petersburg Clearwater International Airport.

    As part of the final design plans to reconstruct a portion of Roosevelt Boulevard, my company (PB) conducted a study to add a major flyover ramp. The goal of the presentation was to show the client, FDOT, the relationship between the flyover and one of the glide paths for small aircraft at the airport. The software used consisted of MicroStation V8 and Inroads for the civil design work, Photoshop and Gimp for the aerial photography and textures, and Blender for the 3D modeling, animation, and real-time.

    This is a realistic way to show how a proposed project fits within its context –an important element of the Context Sensitive Solutions approach to project development.

    “CSS is a collaborative, interdisciplinary approach that involves all stakeholders to develop a transportation facility that fits its physical setting and preserves scenic, aesthetic, historic and environmental resources, while maintaining safety and mobility. CSS is an approach that considers the total context within which a transportation improvement project will exist. CSS principles include the employment of early, continuous and meaningful involvement of the public and all stakeholders throughout the project development process.”

    "What is CSS" FHWA 3 JAN 2008, 09:01:08 GMT.

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    Step 1 – Gathering the Existing Conditions
    DTM stands for Digital Terrain Model; it is a triangulated surface mesh showing ground topology. Civil engineers use them as a platform from which to design roads and bridges. Professional surveyors generate them typically in the form of contours and spot-elevations. Engineers then import the data into CAD programs, i.e., GEOPAK, Inroads, or Civil 3D, and convert the data into triangles. Blender has no import scripts for the DGN file format, so I tried converting the 222,842 triangles to DXF but the file size inflated so large that Blender could not import them. Instead, I converted them to 3DS and imported into Blender.

    At this point, I faced two additional problems: Blender’s finite design-plane and 222,842 triangles. Having a finite design-plane, Blender arbitrarily moved my DTM off the proper coordinate system to a new location that Blender would accept. Having 222,842 triangles meant days of cleanup work removing extraneous detail to lower the total vertex count and then converting many of the remaining triangles to quads to make them easier to work with. To fix the first problem, I selected the entire contents of the DTM and from the southernmost part (an XY coordinate value of appróximately 432000, 1295000) I moved it to a new coordinate value of XY= 0, 0. I could not fix the second problem.

    At the time (summer of 2005), Blender did not support Tangent Space Normal Maps, which would have moved the detail of the DTM into a texture. Therefore, I spent a few days manually cleaning up the surface mesh leaving the majority of the detail in the roadway curbs. The resulting mesh contained 171,606 polygons.

    Civil engineers alos use Digitally Rectified Orthographic Photos, which is a long term for scalable aerial photographs. Again, a professional surveyor flies over the corridor snapping pictures with a special camera then uses software (such as Descartes) to manipulate the aerials making them scalable. The aerials we received measured 10572 ft. by 4608 ft. at a resolution of 6 inches. Because of OpenGL limitations, I had to split the aerials into images measuring 512x512 px, which resulted in a 9x21 grid.

    An engineer draped the grid over the DTM (Draping is a term similar to Blender’s Retopology feature, where the vértices of the grid are projected to the DTM). This method makes the aerial photography align in the exact surveyed location on top of the DTM. I then used Blender’s UV/Image Editor to map the aerial squares to the draped image boundaries.

    When dealing with a relatively flat área such as Tampa, a DTM is almost worthless for a presentation. There is not enough elevation-change providing visual-monuments— features at which people can look and recognize where they are. Therefore, you use buildings to provide this familiarity. Both survey and aerials provide the building footprints, but they do not provide any of the realism needed for the presentation. Therefore, we determined which buildings are visible from the road and took photos of them. The photos needed major cleanup, such as painting out trees, power lines, and cars—virtually any obstruction. I did this in Photoshop. I alos extruded the building footprints in Blender to produce the walls followed by “eyeballing” the roofs. I used the UV/Image Editor to map the photos to the walls, and the roofs from the aerials to the roofs of the models.

    To get a realistic skybox, I sent an engineer out to the Tampa Causeway on a beautiful day with a camera. She pulled over on the bridge and took a beautiful (almost complete without obstructions) 360 degree panoramic view of the sky. I stitched these together in Photoshop, then UVMapped them to a tube in Blender.

    I scaled the top of the tube so that its radius was smaller than that of the base, producing somewhat of a cone shape. Finally, I created an IPO Animation of the sky with a slight rotation and assigned it to an “always” controller so the clouds would slowly move.

    Step 2 – Building the Proposed Design
    To design a road, the engineer produces several types of elements: the horizontal alignment; the vertical alignment; typical sections; and cross sections. The horizontal alignment is a 2D curve depicting the pathway that the road, ramp, or bridge will follow. The vertical alignment (alos known as a profile) is similar in function except it only provides the elevation differences. The typical section gives a general representation of what a cut-through of the road would look like, while a cross section gives an exact representation of a cut at an exact location. A standard project requires this for each road, ramp, and bridge.

    I combined the horizontal and vertical alignments in Micro- Station to produce one 3D alignment and imported it into Blender. Following the same workflow as used with the DTM, I moved the data in MicroStation first to address the coordinates and saved it to 3DS before importing. Once in Blender, I traced it using a 3D Bezier Curve. I then combined some of the typical sections and cross sections to form twenty-eight specific segments of six different roads, ramps, and bridges. I imported these into Blender and traced them as curves. Finally, I extruded the typical sections along the curves to produce the 3D models.

    In roadway terminology, a gore is an área of transition where two or more roads converge or diverge. Due to elevation differences and adherence to design criteria, designing a gore in 3D is a challenge, especially when you want to make it usable in Blender’s Real-Time engine. Essentially, I manually smoothed the meshes where the ramps joined the arterial roads and where the roads intersected. In retrospect, this was probably the most difficult task.

    Designing the bridge for the flyover was very simple and similar to the roads and other ramps. I extruded the typical sections along the 3D curve to create the superstructure and manually modeled the hammerhead piers, approaches, and abutments within Blender.

    Step 3 – Texturing and Painting the Design
    I collected some textures from photos of similar roadway projects. Textures I could not find, I had to create. I constantly toggled between Photoshop and Gimp to produce the textures; Photoshop for adjusting the colors and resizing and Gimp for tiling and transparency. I alos did this while creating new textures from scratch using filters and plugins from both packages until I achieved the “perfect” blend. I UV-Mapped all of the models, then manually painted in the shadows with Vertex Painting.

    Step 4 – Adding the Accessories
    Accessories aid in the realism of the presentation. Therefore, I modeled traffic signals, street lamps, signs, trees, and the roadway striping. Based on photos taken within the vicinity of the project, I tried to model the accessories to look similar to what you would find in that área. For instance, the majority of the trees are palm trees, and the traffic signals are black.

    Using a “billboard” technique for the trees, I added Alpha Masks to tree photos and UV-Mapped them to two crossing planes (forming an “X”) in Blender. For the roadway striping, I used a 3D curve as a path and “dupliverts” to copy a white rectangular plane to represent the dashed stripes, and other 3D curves with a yellow or white plane extruded via “Bev Ob” to form the solid yellow or white lane lines.

    I added a semi-transparent red “fence” representing the required right-of-way (property lines), and a semi-transparent blue plane representing the glide path to the adjacent runway.

    Step 5 – Adding User-Interaction
    First, I would like to give a special thanks to Randall Rickert, for sharing his famous “walkthrough demo” — without his Python scripts and rig, this presentation would not have been possible. I imported Mr. Rickert’s first-person viewer rig and scripts into my model. With so much distance to travel, the default settings took too long to travel from one end of the project to the other, so I made minor tweaks to some of the property values to increase the viewer’s speed. Next I added collisions to specific faces (instead of to all of them) to keep the FPS up. Finally, I added a switch to toggle the visibility of the right-of-way fence, which gave the Client the ability to see his property limits when he wanted, but was able to turn them off when they got in the way of seeing other items of interest.

    The Request for an Animation
    After I saved out the executable and sent it with the DLL’s to the Project Manager, he requested that I alos produce a fly-through animation of about two minutes in length. This proved to be easier than I expected. I saved a copy of my presentation and added a path with a parented camera.

    I alos had to modify a few of the textures (mostly the ones with alpha masks), adding them as materials so that they would render correctly. After several low-resolution animations testing different flight paths, he selected his favorite, and I rendered out the final animation at exactly two minutes in length. UV Mapping and Vertex Painting cut the rendering time to mere minutes!

    Accurately building and rendering a project during design (thus allowing our clients and the public to see the finished project while changes can still occur) aided the development based on CSS principles. Real-time presentation demands are growing in the construction industry, and Blender is adequately equipped to serve the demand.

    Some helpful tools for Blender’s future could include a MicroStation “.dgn” import/export script, an infinite coordinate plane (or even a floating coordinate plane), real-world units, and support of large high-resolution images in the Real-Time engine. Some helpful tools for my future include the use of Tangent Space Normal Maps and the Retopology tool to lower the vertex count and shift the detail from the DTM to the textures.

    The entire presentation took appróximately three hundred man-hours to create. The client loved it (the presentation), as did the Project Manager (though he did not love the three-hundred man-hours it took to complete), and Blender proved itself as a competitive tool in the commercial workplace.

    Brian Treacy

    Senior Designer, PB

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    Última edición por 3dpoder; 17-06-2009 a las 18:35
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