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As of 7 March 2004, this article has been restarted with new base content. All the content was copied over from this Everything2 writeup, with the author's permission. Credit to Simon "fraggle" Howard for his generous contribution of an excellent article! Fredrik 20:21, 7 Mar 2004 (UTC)
The article mentions other games "produced by licensees" using the Doom engine but does not list them. Perhaps someone could list them, or make a list at another article and link it? Some guy 20:36, 13 October 2005 (UTC)
Binary Space Partitioning was first used on Quake, not Doom. The Doom games uses a technology called RayCasting, also invented by Carmack. —Preceding unsigned comment added by 83.254.5.211 ( talk) 09:01, 30 January 2009 (UTC)
RayCasting is the render algorithm, while BSP was the data structure used in order to narrow (minimize) the number of data to process each frame. —Preceding unsigned comment added by 201.222.214.252 ( talk) 15:47, 13 November 2009 (UTC)
The Doom engine using ray casting seems to be a common misconception. The Doom renderer uses a BSP tree in order to find and sort wall segments from near to far. The segments are drawn near to far by finding the distance to the left and right side of the wall and using linear interpolation for the values in between. Where the walls are drawn, top and bottom occulsion variables are set up to prevent far walls from being drawn over near walls (which means the renderer has no over draw until masked (transparent) elements are drawn). The top and bottom of the wall is also used to generate visplane information for drawing the floors in a separate pass. At no point does the renderer ever have to cast a ray in order to determine where the first intersection is.
More details on this can be found here: http://fabiensanglard.net/doomIphone/doomClassicRenderer.php
It is worth noting that ray casting is slower than BSP rendering even back in the day. This is the reason Wolfenstein 3D for SNES and derived ports (3DO, Jaguar, and Mac) actually use a similar BSP renderer as well. There's a video of John Carmack playing Wolf3D where he mentions this IIRC. Blzut3 ( talk) 22:22, 9 October 2013 (UTC)
Does anyone know where can i download Doom engine for free ? Some guy 20:36, 31 Augest 2006 (UTC)
As a guess, ID's website. They certainly used to have their Wolfenstein engine there for download.
Hello. According to some other source, id Tech 1 is the Quake engine. On the id Software webpage, id Tech 2 only identify Quake 2 and they dont talk about the 1. So, are you sure about that? If any body can contact id to know the official reference, it can be very helpful. bayo 20:43, 7 November 2007 (UTC)
Would a section on improvements (such as slopes, DECORATE/SOC scripts, OpenGL) from Doom Sourceports be acceptable on this page? - Snip3rNife ( talk) 03:14, 19 February 2008 (UTC)
When you have a sprite or wall texture, it has x,y and z coordinates. When it is not parallel to the coordinate axes, you could have to rotate it first or use the Bresenham algorithm to make it oblique while you store each pixel of the texture into a buffer (iteratively count through each x and y coordinate of the texture and put each pixel with x,y and z coordinates into a buffer). If the player has turned to the side angles, you rotate every pixel of the sprite in oppsite direction(around the position of the player) with the degree of the angle before the projection. You rotate around the coordinate axes using sinus and cosinus. It's like moving each pixel on a circle with the same angle. For example, rotation on the Y axis would be done that way: x2 = x*cos(angle)+z*sin(angle) z2=-x*sin(angle)+z*cos(angle) y2=y .
After the rotation, you put each pixel on the screen using a central projection. This is very simple. To get the x coordinate of the pixel on the screen, you subtract the X-position of the projection point ( here: the player X-coordinate) from the X-position of the object pixel. Then you divide it by the Z difference ( object Z minus player Z ) and multiply it with a scale factor. Then you do the same thing with the y coordinate. The results are then added to the middle of the screen and then you got it placed on the screen. For example:
x_screen=(screenXresolution/2)+scale*-1*(object.x-cam.x)/z; y_screen=(screenYresolution/2)+scale*-1*(object.y-cam.y)/z;
Values can also be signed. z is not the absolute z value, but the z value relative to the camera position. If z is signed, the pixel will not be put on the screen because it is behind the camera/player.
After you have brought the color value of the pixel on the screen, you store it's old z value for it's screen coordinates in a buffer. Next time a pixel will only be set on the same screen position when it's z value is smaller than the old one. And players and enemies are only scaled sprites. This is the reason they don't rotate when you try to watch them from the side. They could have used different sprites in dependance from the angle, but they were sloppily under time pressure.
You can also count the number of pixels set and abort the "rendering" when the screen is full. You'll have to combine that with a coarse sorting of the texture walls according to the distance from the player. A lot of speed can be gained when you size down the resolution of the textures the bigger their distance from the player is before transferring them into the buffer. Sometimes z is too small so there would be gaps on the screen. Then you only have to put several pixels next to each other (depending how many) on z and also note that in the z buffer.
Also the player movements will be done with a rotatable vector. You'll figure it out. It's simple. 10th grade knowledge.
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As of 7 March 2004, this article has been restarted with new base content. All the content was copied over from this Everything2 writeup, with the author's permission. Credit to Simon "fraggle" Howard for his generous contribution of an excellent article! Fredrik 20:21, 7 Mar 2004 (UTC)
The article mentions other games "produced by licensees" using the Doom engine but does not list them. Perhaps someone could list them, or make a list at another article and link it? Some guy 20:36, 13 October 2005 (UTC)
Binary Space Partitioning was first used on Quake, not Doom. The Doom games uses a technology called RayCasting, also invented by Carmack. —Preceding unsigned comment added by 83.254.5.211 ( talk) 09:01, 30 January 2009 (UTC)
RayCasting is the render algorithm, while BSP was the data structure used in order to narrow (minimize) the number of data to process each frame. —Preceding unsigned comment added by 201.222.214.252 ( talk) 15:47, 13 November 2009 (UTC)
The Doom engine using ray casting seems to be a common misconception. The Doom renderer uses a BSP tree in order to find and sort wall segments from near to far. The segments are drawn near to far by finding the distance to the left and right side of the wall and using linear interpolation for the values in between. Where the walls are drawn, top and bottom occulsion variables are set up to prevent far walls from being drawn over near walls (which means the renderer has no over draw until masked (transparent) elements are drawn). The top and bottom of the wall is also used to generate visplane information for drawing the floors in a separate pass. At no point does the renderer ever have to cast a ray in order to determine where the first intersection is.
More details on this can be found here: http://fabiensanglard.net/doomIphone/doomClassicRenderer.php
It is worth noting that ray casting is slower than BSP rendering even back in the day. This is the reason Wolfenstein 3D for SNES and derived ports (3DO, Jaguar, and Mac) actually use a similar BSP renderer as well. There's a video of John Carmack playing Wolf3D where he mentions this IIRC. Blzut3 ( talk) 22:22, 9 October 2013 (UTC)
Does anyone know where can i download Doom engine for free ? Some guy 20:36, 31 Augest 2006 (UTC)
As a guess, ID's website. They certainly used to have their Wolfenstein engine there for download.
Hello. According to some other source, id Tech 1 is the Quake engine. On the id Software webpage, id Tech 2 only identify Quake 2 and they dont talk about the 1. So, are you sure about that? If any body can contact id to know the official reference, it can be very helpful. bayo 20:43, 7 November 2007 (UTC)
Would a section on improvements (such as slopes, DECORATE/SOC scripts, OpenGL) from Doom Sourceports be acceptable on this page? - Snip3rNife ( talk) 03:14, 19 February 2008 (UTC)
When you have a sprite or wall texture, it has x,y and z coordinates. When it is not parallel to the coordinate axes, you could have to rotate it first or use the Bresenham algorithm to make it oblique while you store each pixel of the texture into a buffer (iteratively count through each x and y coordinate of the texture and put each pixel with x,y and z coordinates into a buffer). If the player has turned to the side angles, you rotate every pixel of the sprite in oppsite direction(around the position of the player) with the degree of the angle before the projection. You rotate around the coordinate axes using sinus and cosinus. It's like moving each pixel on a circle with the same angle. For example, rotation on the Y axis would be done that way: x2 = x*cos(angle)+z*sin(angle) z2=-x*sin(angle)+z*cos(angle) y2=y .
After the rotation, you put each pixel on the screen using a central projection. This is very simple. To get the x coordinate of the pixel on the screen, you subtract the X-position of the projection point ( here: the player X-coordinate) from the X-position of the object pixel. Then you divide it by the Z difference ( object Z minus player Z ) and multiply it with a scale factor. Then you do the same thing with the y coordinate. The results are then added to the middle of the screen and then you got it placed on the screen. For example:
x_screen=(screenXresolution/2)+scale*-1*(object.x-cam.x)/z; y_screen=(screenYresolution/2)+scale*-1*(object.y-cam.y)/z;
Values can also be signed. z is not the absolute z value, but the z value relative to the camera position. If z is signed, the pixel will not be put on the screen because it is behind the camera/player.
After you have brought the color value of the pixel on the screen, you store it's old z value for it's screen coordinates in a buffer. Next time a pixel will only be set on the same screen position when it's z value is smaller than the old one. And players and enemies are only scaled sprites. This is the reason they don't rotate when you try to watch them from the side. They could have used different sprites in dependance from the angle, but they were sloppily under time pressure.
You can also count the number of pixels set and abort the "rendering" when the screen is full. You'll have to combine that with a coarse sorting of the texture walls according to the distance from the player. A lot of speed can be gained when you size down the resolution of the textures the bigger their distance from the player is before transferring them into the buffer. Sometimes z is too small so there would be gaps on the screen. Then you only have to put several pixels next to each other (depending how many) on z and also note that in the z buffer.
Also the player movements will be done with a rotatable vector. You'll figure it out. It's simple. 10th grade knowledge.
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Cheers.— InternetArchiveBot ( Report bug) 19:28, 15 December 2016 (UTC)
Hello fellow Wikipedians,
I have just modified one external link on Doom engine. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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Cheers.— InternetArchiveBot ( Report bug) 14:19, 22 January 2018 (UTC)