The env_sprite entity allows you to render sprites, which are common 2D-graphics which will appear aligned to face you at all times, unless specified otherwise.
OnDestroy Function ondestroyfn : Name of the function to use from already parsed .as script files when entity is destroyed (killed) in any way. If the function belongs to namespace, you must use prefix with the namespace name (e.g. mynamespace::MyFunction) for the keyvalue.
Name targetname : Set name of env_sprite so other entities can trigger it to enable or disable sprite. Depending on trigger use-type: 'On'- show sprite, 'Off'- hide sprite, 'Toggle'- toggle sprite. Can be kill-targeted.
Render FX renderfx : Set custom render FX effect. Only works when "Render Mode" is set to different than 'Normal'
Render Mode rendermode : Render mode determines how this entity is rendered.
FX Amount (1 - 255) renderamt : Render amount to use when other than "Render Mode" 'Normal' is used.
FX Color (R G B) rendercolor : Used with "Render Mode" 'Color' and 'Glow' to set color. Also sets color of 'Glow Shell' "Render Mode".
Pitch Yaw Roll (X Y Z) angles : Where Z means Y and Y means Z, that is, when you're thinking Hammer-grid. (Hammer uses Z for height and Y for depth, while every other sane 3D-application does this the other way round; nonetheless this keyvalue description has the letters in the conventional order) This, technically, is a 3D-vector containing Euler-angles to describe either the entity's rotation or direction of effect. E.g. a func_door_rotating will use this as its initial rotation, while a trigger_push will keep its original alignment and use this for the direction of its push-effect instead. Euler-angles are a hierarchical system to determine an object's orientation in 3D-space. A yaw-value of 0 would mean the entity would face east. (right in top-down view) 90 would mean it would face north. (up in top-down-view) After yaw, pitch is applied. Think aiming up/down with your character in first person. At last, the roll-value is applied. Think your character falling over sideways in first person. Some entities, mostly point entities, do not use the angles keyvalue for any purpose.
Framerate framerate : Sprite framerate.
Sprite Name model : Set a sprite to be displayed. Path start in modification's folder.
Scale scale : Set the scale of the sprite effect. This defaults to 0.25 if not set.
Draw Type / Orientation vp_type : Feature that allows to override view port of the sprite.
1 : Start on : Causes the env_sprite effect to be visible from map-load onwards. Useful when the env_sprite has a targetname. Makes little to no sense in combination with "Play Once".
2 : Play Once : If set, the sprite animation won't loop and end after cycling through all of its frames once. If the sprite is not animated, only the first frame will show for a moment.
4 : Once + Remove : If set along with "Play once", causes the env_sprite entity to be removed from the game after having played. Useful for saving some entities.
2048 : Not in Deathmatch : Obsolete in Sven Co-op. Makes the entity don't appear in Multiplayer Games.
To make sprite work properly use "Render Mode" with optional "FX Amount". Most sprites can make use of 'Glow' or 'Additive' render modes (most sprites are in 'additive' format), however sprites with 'alphatest' works best with 'Texture' mode (background gets removed, image is opaque), while 'indexalpha' sprites are rendered properly only in 'Solid' and 'Texture', in any other mode they appearance is invalid. You can use third party tools like Sprite Explorer to check format of sprite if you are not sure, or check this Sprite List to check format type each sprite.
Sprite alignment can also be set through the sprite itself. To do this, edit byte at offset 8 (meaning the 9th byte) in the sprite file using a HEX editor: 00: Sprite fixed on vertical axis- SPR_VP_PARALLEL_UPRIGHT; 01: Not supported- SPR_FACING_UPRIGHT; 02: Normal behaviour, sprite always faces you- SPR_VP_PARALLEL; 03: Sprite is fixed in space and can be rotated using angles- SPR_ORIENTED; 04: As SPR_VP_PARALLEL, but sprite can be rotated relatively to perspective using angles- SPR_VP_PARALLEL_ORIENTED.
Oriented mode sprites tend to have problems with angle co-ordinates in hammer so its best to set them manually starting from [180,180,180] instead of [0,0,0]. In addition don't use negative numbers; instead subtract from 360. Also use 360 instead of 0 and carefully watch the use of hammer transforms as it will likely give you numbers that might look fine in hammer but will not work in-game. If you are still having troubles with angles not appearing in map I have an example RMF included in the example file download at the bottom (called "oriented_angles.rmf"). Taken from: http://www.the303.org/tutorials/gold_sprite.htm.
There is no key as of yet to set the initial frame of the env_sprite for it to draw. This must be done manually by changing the env_sprite's "frame" key via trigger_changevalue.