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author= Mark Moxon;
description= Fully documented source code disassembly for Lander on the Acorn Archimedes, with lots of deep dive articles explaining how every aspect of the game works.;
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software archaeology projects fully documented source code for elite on the bbc micro acorn electron commodore 64 apple ii and nes fully documented source code for aviator on the bbc micro fully documented source code for revs on the bbc micro fully documented source code for the sentinel on the bbc micro right on commanders mark moxon x all of my sites are 100 handcrafted i have not used ai at any point in any of my projects there s a good reason for this ai isn t a very good fit for what i do for me one of the main attractions of working with old computers is that it is possible for one person to understand every single layer electrons logic gates ics cpus operating systems and classic games i try to keep it this way when i create my disassemblies and hacks and deep dives i love that fact that it s me working things out i don t want help i just want a set of manuals and a simple development environment that doesn t get in the way this is my handcrafted happy place i don t want to delegate any of it if i m being honest of course some of the modern development tools i use have been built with ai and very good they are too but they re typically emulators or disc imagers that replicate the functionality of old computers rather than providing ai functionality themselves my projects may be ai free but they obviously exist in a world that isn t visit my software archaeology site to find out more about the tools i use lander written by david braben d j braben 1987 commentary mark moxon 2021 all rights reserved home page using this site home page start at the very beginning quick start guide all you need to know to start exploring this site all about this project project history building the source and more all about this project about this project the story of how this project came to be terminology used in this commentary read this before you explore the source code building lander from the source how to build your own working copy of lander useful links a collection of links to pages i ve found useful during this project acknowledgements the giants on whose shoulders this project stands site history a short history of this site s development site map a top level map of this website to do list code that could benefit from a bit more analysis playing with the lander source code playing lander in the 21st century how to play all the versions of lander analysed here deep dive articles over 20 articles on how lander weaves its magic index index of all deep dive articles discover how lander works under the hood deep dives program structure memory maps and the main game loop program structure the lander memory map memory usage and squeezing lander into the unexpanded archimedes 305 the main game loop details of the tasks that lander performs every iteration around the main loop landscape how the luscious 3d landscape is created landscape the camera and the landscape offset an explanation of two fundamental aspects of the lander drawing routines generating the landscape using fourier synthesis to generate a 3d landscape using simple trigonometry drawing the landscape converting a set of altitudes into an undulating landscape of coloured tiles 3d objects and particles drawing 3d objects and simulating particle physics 3d objects and particles object blueprints storing 3d object definitions using vertices faces and normals drawing 3d objects drawing 3d objects using object blueprints and rotation matrices placing objects on the map details of lander s object types and the object map particles and particle clouds the particles that make up sparks splashes explosions and exhaust plumes flight the challenges of travelling by mouse flight flying by mouse flying the ship in lander using polar coordinates and thrust vectors collisions and bullets detecting when the player has crashed or shot down an object drawing on the screen how lander s graphics make it onto the screen drawing on the screen depth sorting with the graphics buffers the clever bin sorting hack that correctly displays objects behind one another drawing triangles building a landscape and 3d objects out of nothing but triangles projecting onto the screen how lander converts 3d world coordinates into 2d screen coordinates screen memory in the archimedes understanding vidc colours and bank switching on the archimedes miscellaneous exploring this important piece of coding history miscellaneous random numbers lander uses a random number algorithm from the arm evaluation system in david braben s own words a code analysis of the lander author s own article from the micro user comparing lander to zarch how lander s big brother compares to its predecessor unused code in lander memory might be tight but even lander contains some hidden subroutines lander s origins on the arm1 how the creation of lander on the arm1 influenced the code hacking the landscape hacking the lander source to create huge landscapes on faster machines exploring the lander source code lander source code annotated source of lander version information about the version of lander on this site details of the different versions of lander lander source code by file map of the source code an overview of how the source code for lander is structured annotated source files the fully commented source files lander source files workspaces and configuration the main variable workspaces used in lander lander a source part 1 of the main game code lander b source part 2 of the main game code lander c source part 3 of the main game code lander d source part 4 of the main game code runimage source the runimage source for risc os lander source code by category 3d objects 3d objects such as trees buildings and ships subroutines drawobject part 1 of 5 draw a 3d object and its shadow drawobject part 2 of 5 process the object s vertices drawobject part 3 of 5 calculate the visibility of each of the object s faces drawobject part 4 of 5 draw the shadow for each of the object s faces drawobject part 5 of 5 draw each of the object s faces drawobjects part 1 of 3 draw all the objects in the visible portion of the object map starting by working our way through the map looking for objects drawobjects part 2 of 3 draw the object that we have found on the object map drawobjects part 3 of 3 draw a destroyed object that we have found on the object map placeobjectsonmap randomly place a number of objects on the map avoiding the sea and the launchpad variables objectbuilding object blueprint for the building objectfirtree object blueprint for the fir tree objectgazebo object blueprint for the gazebo objectplayer object blueprint for the player s ship objectplayeraddr the address of the object blueprint for the player s ship objectpyramid object blueprint for a pyramid objectrock object blueprint for a rock objectrockaddr the address of the object blueprint for a rock objectrocket object blueprint for the rocket objectsmallleafytree object blueprint for the small leafy tree objectsmokingbuilding object blueprint for the smoking remains of a building objectsmokinggazebo object blueprint for the smoking remains of a gazebo objectsmokingremainsleft object blueprint for the smoking remains that bend to the left objectsmokingremainsright object blueprint for the smoking remains that bend to the right objecttallleafytree object blueprint for the tall leafy tree objecttypes a table that maps object types to object blueprints copy protection hiding the lander code from prying eyes subroutines decryptgamebinary runimage placeholder routine to decrypt game code to 8000 so it can be run runimageentry runimage entry point for the runimage absolute file variables absoluteaddr runimage the address of the start of the absolute file gamecode runimage the unencrypted game code gamecodeaddr runimage the address of the game code gamecodeendaddr runimage the address of the end of the game code drawing lines the core horizontal line drawing routines subroutines drawhorizontalline draw a horizontal line drawlinesegment draw a horizontal line of between 0 and 17 pixels by jumping to the relevant entry point variables linejump jump table for drawing a horizontal line of between 0 and 17 pixels using the relevant entry point in drawlinesegment drawing the screen smooth animation using screen switching subroutines switchscreenbank switch screen banks and clear the newly hidden screen bank to black variables greycolourwords an unused table of grey four pixel colour words greycolourwordsaddr the unused address of the unused table of grey four pixel colour words screenaddr the screen address for the start of the 17th pixel line in the current bank i e the line just below the two rows of text screenbank1addr the screen address for the start of the 17th pixel line in screen bank 1 i e the line just below the two rows of text screenbank2addr the screen address for the start of the 17th pixel line in screen bank 0 i e the line just below the two rows of text screenbanknumber the number of the current screen bank 0 or 1 drawing triangles the main building block of the 3d world subroutines drawquadrilateral draw a quadrilateral i e two triangles drawtriangle part 1 of 11 draw a triangle starting by ordering the coordinates and jumping to the relevant part of the routine drawtriangle part 2 of 11 calculate the slope of x1 y1 to x2 y2 drawtriangle part 3 of 11 calculate the slope of x1 y1 to x3 y3 drawtriangle part 4 of 11 draw a triangle that isn t clipped and has a sloping first side drawtriangle part 5 of 11 draw a triangle with a horizontal edge between x1 y1 and x2 y2 drawtriangle part 6 of 11 draw a clipped triangle that s partly off screen drawtriangle part 7 of 11 calculate the slopes of x1 y1 to x2 y2 and x1 y1 to x3 y3 for a clipped triangle drawtriangle part 8 of 11 draw the bottom part of a clipped triangle drawtriangle part 9 of 11 draw the top part of a clipped triangle drawtriangle part 10 of 11 draw a clipped triangle with a horizontal edge between x1 y1 and x2 y2 drawtriangle part 11 of 11 draw a triangle clipping it to the screen as we go drawtrianglefrombuffer process the draw triangle command from the graphics buffer drawtriangleshadowtobuffer draw a triangle shadow into the correct graphics buffer according to its distance drawtriangletobuffer draw a coloured triangle into a slightly nearer graphics buffer according to its distance graphics buffers how lander draws objects in distance order subroutines addterminatorstobuffers add terminators to the ends of the graphics buffers so we know when to stop drawing drawgraphicsbuffer draw the contents of the specified graphics buffer variables bufferjump the jump table for drawing commands that we store in the graphics buffers graphicsbuffendaddr2 the addresses of the tables containing the graphics buffer addresses same as graphicsbufferendaddr and graphicsbufferaddr graphicsbufferaddr the address of the table containing the addresses of the graphics buffers graphicsbufferendaddr the address of the table containing the end addresses of the graphics buffers graphicsbuffers the addresses of each of the graphics buffers these values do not change graphicsbuffersend the end addresses of each of the graphics buffers these values get updated as objects are drawn into the buffers landscape the secrets of lander s undulating landscape subroutines drawlandscapeandbuffers part 1 of 4 draw the landscape and the contents of the graphics buffers from the back of the screen to the front drawlandscapeandbuffers part 2 of 4 draw a row of landscape tiles drawlandscapeandbuffers part 3 of 4 draw the objects in the graphics buffers for two rows behind the current corner row drawlandscapeandbuffers part 4 of 4 draw the remaining graphics buffers getlandscapealtitude calculate the altitude of the landscape for a given coordinate getlandscapebelowvertex calculate the landscape altitude directly below an object s vertex getlandscapetilecolour calculate the colour of the landscape tile currently being drawn variables landscapeconfig the configuration data for each tile row in the landscape landscapeconfigaddr the address of the landscapeconfig table landscapeoffset the offset we apply to the on screen landscape to push it away from us and to the left so the visible tiles fit nicely on screen landscapeoffsetaddr the address of the landscape offset main loop the core game loop that runs lander subroutines endgame finish the game gameover print a game over message and start a new game loselife display a crash animation when we lose a life and end the game if this is our last life loselifefromparticleloop lose a life when a crash is detected in the particle processing loop mainloop the main game loop startnewgame start a brand new game with a full set of lives and a newly generated set of objects maths arithmetic division square roots and random numbers subroutines getrandomnumbers generate pseudo random numbers from the random number seeds variables divisiontable division lookup tables divisiontableaddr the address of the division lookup table randomseed1 the first random seed for the random number generator randomseed2 the second random seed for the random number generator squareroottable square root lookup table squareroottableaddr the address of the square root lookup table maths geometry trigonometry vectors and rotation matrices subroutines addvectors an unused routine that adds two vectors and uses self modifying code to store the results in a specified location addvectorswithfeedback an unused routine that adds a delta vector to a coordinate and updates the delta with feedback from the coordinate value addvectortovertices add a vector to the rotated vertex coordinates to get the vertex coordinates in 3d space calculaterotationmatrix calculate the rotation matrix getdotproduct calculate the dot product of two 3d vectors getmouseinpolarcoordinates part 1 of 2 convert the mouse x and y coordinates into polar coordinates starting by calculating the polar angle getmouseinpolarcoordinates part 2 of 2 calculate the polar distance multiplyvectorbyconstant an unused routine that multiplies a vector by a constant value multiplyvectorbymatrix multiply a 3d vector by the rotation matrix in rotationmatrix if the object is a rotating object projectparticleontoscreen project a 3d particle coordinate onto the screen projectvertexontoscreen project a vertex coordinate from a 3d object onto the screen transposerotationmatrix an unused routine that transposes the rotation matrix variables arctantable arctan lookup table arctantableaddr the address of the arctan lookup table sintable sine cosine lookup table sintableaddr the address of the sine cosine lookup table particles explosions splashes sparks and falling rocks subroutines addbulletparticletobuffer add a bullet particle to the particle data buffer adddebrisparticletobuffer add a debris particle to the particle data buffer which is a purple brownish green particle that bounces out of an explosi...
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