From 782561e869ec1a80fa2cd5690212936f2098f7d9 Mon Sep 17 00:00:00 2001
From: Jaycie Ewald <jaycie.ewald@outlook.com>
Date: Thu, 7 Dec 2023 19:08:08 -0600
Subject: [PATCH] Add angled sprite code from QuakeSpasm and FTEQW

---
 Quake/gl_model.c |  6 ++++--
 Quake/r_sprite.c | 13 +++++++++++++
 Quake/spritegn.h |  2 +-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Quake/gl_model.c b/Quake/gl_model.c
index 766299b38..036f46d5f 100644
--- a/Quake/gl_model.c
+++ b/Quake/gl_model.c
@@ -3234,7 +3234,7 @@ static void *Mod_LoadSpriteFrame (void * pin, mspriteframe_t **ppframe, int fram
 Mod_LoadSpriteGroup
 =================
 */
-static void *Mod_LoadSpriteGroup (void * pin, mspriteframe_t **ppframe, int framenum)
+static void *Mod_LoadSpriteGroup (void * pin, mspriteframe_t **ppframe, int framenum, spriteframetype_t type)
 {
 	dspritegroup_t		*pingroup;
 	mspritegroup_t		*pspritegroup;
@@ -3246,6 +3246,8 @@ static void *Mod_LoadSpriteGroup (void * pin, mspriteframe_t **ppframe, int fram
 	pingroup = (dspritegroup_t *)pin;
 
 	numframes = LittleLong (pingroup->numframes);
+	if (type == SPR_ANGLED && numframes != 8)
+		Sys_Error ("Mod_LoadSpriteGroup: Bad # of frames: %d", numframes);
 
 	pspritegroup = (mspritegroup_t *) Hunk_AllocName (sizeof (mspritegroup_t) +
 				(numframes - 1) * sizeof (pspritegroup->frames[0]), loadname);
@@ -3349,7 +3351,7 @@ static void Mod_LoadSpriteModel (qmodel_t *mod, void *buffer)
 		else
 		{
 			pframetype = (dspriteframetype_t *)
-					Mod_LoadSpriteGroup (pframetype + 1, &psprite->frames[i].frameptr, i);
+					Mod_LoadSpriteGroup (pframetype + 1, &psprite->frames[i].frameptr, i, frametype);
 		}
 	}
 
diff --git a/Quake/r_sprite.c b/Quake/r_sprite.c
index 453b4f186..2ca008024 100644
--- a/Quake/r_sprite.c
+++ b/Quake/r_sprite.c
@@ -89,6 +89,19 @@ mspriteframe_t *R_GetSpriteFrame (entity_t *currentent)
 	{
 		pspriteframe = psprite->frames[frame].frameptr;
 	}
+	else if (psprite->frames[frame].type == SPR_ANGLED)
+	{
+		// erysdren - angled sprites code backported from FTEQW
+		vec3_t axis[3];
+		AngleVectors(currentent->angles, axis[0], axis[1], axis[2]);
+		{
+			float f = DotProduct(vpn, axis[0]);
+			float r = DotProduct(vright, axis[0]);
+			int dir = (atan2(r, f)+1.125*M_PI)*(4/M_PI);
+			pspritegroup = (mspritegroup_t *)psprite->frames[frame].frameptr;
+			pspriteframe = pspritegroup->frames[dir&7];
+		}
+	}
 	else
 	{
 		pspritegroup = (mspritegroup_t *)psprite->frames[frame].frameptr;
diff --git a/Quake/spritegn.h b/Quake/spritegn.h
index 1065052f0..817484286 100644
--- a/Quake/spritegn.h
+++ b/Quake/spritegn.h
@@ -104,7 +104,7 @@ typedef struct {
 	float	interval;
 } dspriteinterval_t;
 
-typedef enum { SPR_SINGLE=0, SPR_GROUP } spriteframetype_t;
+typedef enum { SPR_SINGLE=0, SPR_GROUP, SPR_ANGLED } spriteframetype_t;
 
 typedef struct {
 	spriteframetype_t	type;