12
$\begingroup$

https://ohiostate.pressbooks.pub/graphicshistory/chapter/13-4-nasa/ says that cgi was used for Apollo trainers. I just want to know the quality of this cgi.

A modern computer runs at 2560 lines on 200 gflops and 100 fps. Apollo footage is on 320 lines and 10 fps. So 640x less computation. Since a 1968 computer was 5 mflops, I think you would need about 50 of them to do realtime photorealistic rendering for Apollo.

The Apollo training systems could have relied on cgi exclusively, they could have used other techniques exclusively, or they could have used a mix of cgi and other techniques such as cameras and models. If they used cgi, what was the quality of that cgi (resolution/frame rate)?

| improve this question | |
$\endgroup$
  • 1
    $\begingroup$ Evans & Sutherland was founded in 1968. Rendering pictures was difficult but not impossible in this time. The problem may be reduced by avoiding the hidden lines detection. $\endgroup$ – Uwe Jul 29 '18 at 16:09
  • 3
    $\begingroup$ I've never encountered this claim before. AFAIK, the visual component of Apollo simulations was done with computer-controlled cameras and models - much simpler and more accurate given the state of the art at the time. $\endgroup$ – Russell Borogove Jul 29 '18 at 16:59
  • 2
    $\begingroup$ It's amusing that the linked article claims the LMS used CGI, yet includes a picture (the "artist's conception") that shows the skycrane visual system to the right of the crew station. $\endgroup$ – Organic Marble Jul 29 '18 at 19:19
  • 2
    $\begingroup$ Even assuming your guess is correct, 50 Apollo-era computers can't do realtime rendering for a simulator. The rendering has to respond to realtime input, while those computers each need 5 seconds to render one frame, so the rendering lags your input by 5 seconds. $\endgroup$ – Hobbes Jul 30 '18 at 16:59
  • $\begingroup$ Not if they're using split frame rendering @Hobbes... $\endgroup$ – JCRM Jul 31 '18 at 13:17
23
$\begingroup$

I think your source is simply incorrect on this.

As far as I know, there was no computer generated graphics (in the modern sense of the term) in Apollo-era simulators. Motion-controlled cameras were used with models and projections to synthesize views optically -- under computer control, but not as digital renderings. EDIT: As JCRM notes, the Lunar Module Procedures Simulator (distinct from the Lunar Module Simulator) did have an "electronic image generator" which could produce crude polygon renderings.

According to Digital Apollo, the main mission simulators each:

comprised a huge "train wreck" of computers, spacecraft hardware, film projectors, models, and analog video equipment.

...

The mission simulators were run by enormous digital computers, several for each, with extensive optical systems to synthesize views outside the windows during missions.

...

The "lunar mission simulator", or LMS, ran off three mainframe computers, and included five tons of glass -- lenses, mirrors, and projectors to accurately recreate the scenes of a landing. Astronauts could practice sighting landmarks, entering data into the computers, and simulate landings from about 12,000 feet to touchdown. As the pilots "flew", computer models of the LM's motions directed a small camera above a physical model of the lunar terrain, sixteen feet in diameter at 1:2000 scale ... A network of servos "flew" the camera over the diorama, right down to the point of landing.

...

A history of simulation technology in the space program has yet to be written, but it would show how the creation of virtual reality preceded, rather than responded to, the creation of real time computer graphics.

Here's a bit of video showing the lunar surface model and camera rig.

@Uwe notes that computer graphics pioneer Evans & Sutherland was founded in 1968; one of their first products was a vector display processor called Line Drawing System 1 and was delivered after Apollo 11 had already flown; motion-controlled camera systems would have been much more practical and higher-fidelity at the time. This is LDS-1:

enter image description here

The practiced eye will discern some subtle artifacts in that rendering which distinguish it from actual Apollo footage.

There's a scene in the film Apollo 13 featuring such a camera system in the simulation of the transposition-docking-extraction maneuver, with nice cuts between the view from the sim cabin and the camera moving towards the target model. Unfortunately I can't find that particular scene on YouTube.

The NASA doc Apollo Experience Report: Simulation of Manned Space Flight for Crew Training covers the design and function of each of the different simulator systems pretty well.

| improve this answer | |
$\endgroup$
  • 5
    $\begingroup$ There was also a servo-controlled "starball" - a sphere studded with ball bearings - to generate the star fields (through some clever optics). One of my colleagues worked on the software that drove the starball. You are correct, there was no computer generated graphics in the AMS. It was extremely primitive even in the shuttle simulator at first and required special purpose computers even for that. $\endgroup$ – Organic Marble Jul 29 '18 at 18:21
  • 3
    $\begingroup$ In fact, the original shuttle simulator (the Approach and Landing Trainer) used a skycrane camera over a model board of Edwards Airforce Base. The mapboard was mounted on the wall and the skycrane flew up and down the wall (as well as having an altitude drive). Shuttle simulator lore holds that when the digital graphics were installed, the squares of the mapboard disappeared quickly to be used as souvenirs. But, an Air Force general wanted it mounted on his office wall, so management had to round up all the segments. $\endgroup$ – Organic Marble Jul 29 '18 at 19:23
  • 1
    $\begingroup$ This article has a picture of the AMS starball. It seems to be in the Smithsonian. airandspace.si.edu/rfp/exhibitions/files/j16-content/… $\endgroup$ – Organic Marble Jul 29 '18 at 19:36
5
$\begingroup$

Here is a lengthy description of the Apollo Mission Simulator visual systems.

It is taken from the Apollo Mission Simulator Instructor Handbook Volume 1. You will note that there is zero CGI equipment mentioned.

enter image description here

enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here

| improve this answer | |
$\endgroup$
3
$\begingroup$

The Committee on Vision Assembly of Behavioral and Social Sciences National Research Council's Working Group 34 reported in 1975

The most elaborate electronically-generated visual simulations available at the present timeare one developed for NASA in connec- tion with the lunar module (Lockwood, 1971) and the space shuttle vehicle (SSV) program, and another currently being developed for the Air Force. [...] It consists of 320 edges. Its 20 Hz. scanning rate and a 600 line raster were designed to gain spatial resolution at the expense of temporal resolution.

As yet I've been unable to chase down the reference:
Lockwood, L. W. Visual simulators for moon men. Optical Spectra,. 1971, 5, No. 8, 32-36.

It is possible, but I think unlikely, the Apollo display was more capable than the Space Shuttle one

320 edges gives around 212 polygons in a tri-mesh.

Edit to add NASA Technical Note D-7112 (1973):

Two general techniques have been used for target-vehicle simuiation: a direct analog system of closed-circuit TV and models, and an electronically generated (drawn) image. In both systems, the input to the display system was through a CRT in the infinity optics systems. The electronic image generator (EIG) was used successfully in one of the Gemini mission simulators, in the Gemini part-task trainer, and in the LMPS. In the EIG system, the target vehicle was drawn on the face of the CRT. The outline or envelope of the target was drawn at a 60-hertz rate; however, the surface was filled in at a 15.75-kilohertz rate. The image generation contained nine degrees of freedom and produced such phenomena as line-of-sight blanking, illumination 20 shadowing, and perspective distortion. Simple target shapes (cylinders, cones, and others) as well as combinations of these shapes were readily simulated with simple surface markings and details [...] Both the TV/model and electronic- image techniques have produced satisfactory displays for stationkeeping and docking. In the EIG technique, complex shapes cannot be drawn; therefore, realism is significantly less. Conversely, the EIG is a much simpler system to maintain and operate.

To address the notion of using early (integrated circuit) transistor technology to produce a "modern" simulation, NASA's 1971 ILLIAC IV managed a staggering 50 MFLOPs on it's 64 cores, but it only had 16k memory available to each core. You'd need 14 cores just to hold the frame buffer

But let's be generous and say with 16 bit addressing it could access a full 64kB, and by some magic of massively parallel computing they can instantly share each others memory you'd need 512 ILLIAC IV's to make a 2GB graphics card. At $31 Million each, that is around three fifths of the entire Apollo budget.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Do you have any more information about the LMPS? It wasn't one of the main training simulators at JSC or KSC. I found a picture of it on the Smithsonian website. Perhaps it was at Grumman, or one of the other centers. I'd love to find out more about it. $\endgroup$ – Organic Marble Jul 30 '18 at 17:08
  • 1
    $\begingroup$ Unfortunately not, @OrganicMarble. It might be the same thing as the LM Dynamic Crew Procedures Trainer at NASA/JSC in Houston; EIG was also used in the Mercury Procedures Simulator $\endgroup$ – JCRM Jul 30 '18 at 17:22
  • $\begingroup$ ILLIAC IV was not built with early discrete transistor technology, it used integrated circuits. $\endgroup$ – Uwe Aug 1 '18 at 21:22
  • $\begingroup$ The ICs were transistor based. One of the big things about ILLIAC IV was it used transistor memory (on chips), as opposed to magnetic core. Trying to do real time graphics on core memory would be... interesting $\endgroup$ – JCRM Aug 1 '18 at 21:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.