src/mesa/main/viewport.c

   1 /*
   2  * Mesa 3-D graphics library
   3  *
   4  * Copyright (C) 2009  VMware, Inc.  All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  22  * OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 /**
  27  * \file viewport.c
  28  * glViewport and glDepthRange functions.
  29  */
  30
  31
  32 #include "context.h"
  33 #include "enums.h"
  34 #include "macros.h"
  35 #include "mtypes.h"
  36 #include "viewport.h"
  37
  38 static void
  39 clamp_viewport(struct gl_context *ctx, GLfloat *x, GLfloat *y,
  40                GLfloat *width, GLfloat *height)
  41 {
  42    /* clamp width and height to the implementation dependent range */
  43    *width  = MIN2(*width, (GLfloat) ctx->Const.MaxViewportWidth);
  44    *height = MIN2(*height, (GLfloat) ctx->Const.MaxViewportHeight);
  45
  46    /* The GL_ARB_viewport_array spec says:
  47     *
  48     *     "The location of the viewport's bottom-left corner, given by (x,y),
  49     *     are clamped to be within the implementation-dependent viewport
  50     *     bounds range.  The viewport bounds range [min, max] tuple may be
  51     *     determined by calling GetFloatv with the symbolic constant
  52     *     VIEWPORT_BOUNDS_RANGE (see section 6.1)."
  53     */
  54    if (ctx->Extensions.ARB_viewport_array ||
  55        (ctx->Extensions.OES_viewport_array &&
  56         _mesa_is_gles31(ctx))) {
  57       *x = CLAMP(*x,
  58                  ctx->Const.ViewportBounds.Min, ctx->Const.ViewportBounds.Max);
  59       *y = CLAMP(*y,
  60                  ctx->Const.ViewportBounds.Min, ctx->Const.ViewportBounds.Max);
  61    }
  62 }
  63
  64 static void
  65 set_viewport_no_notify(struct gl_context *ctx, unsigned idx,
  66                        GLfloat x, GLfloat y,
  67                        GLfloat width, GLfloat height)
  68 {
  69    if (ctx->ViewportArray[idx].X == x &&
  70        ctx->ViewportArray[idx].Width == width &&
  71        ctx->ViewportArray[idx].Y == y &&
  72        ctx->ViewportArray[idx].Height == height)
  73       return;
  74
  75    FLUSH_VERTICES(ctx, ctx->DriverFlags.NewViewport ? 0 : _NEW_VIEWPORT);
  76    ctx->NewDriverState |= ctx->DriverFlags.NewViewport;
  77
  78    ctx->ViewportArray[idx].X = x;
  79    ctx->ViewportArray[idx].Width = width;
  80    ctx->ViewportArray[idx].Y = y;
  81    ctx->ViewportArray[idx].Height = height;
  82 }
  83
  84 struct gl_viewport_inputs {
  85    GLfloat X, Y;                /**< position */
  86    GLfloat Width, Height;       /**< size */
  87 };
  88
  89 struct gl_depthrange_inputs {
  90    GLdouble Near, Far;          /**< Depth buffer range */
  91 };
  92
  93 static void
  94 viewport(struct gl_context *ctx, GLint x, GLint y, GLsizei width,
  95          GLsizei height)
  96 {
  97    struct gl_viewport_inputs input = { x, y, width, height };
  98
  99    /* Clamp the viewport to the implementation dependent values. */
 100    clamp_viewport(ctx, &input.X, &input.Y, &input.Width, &input.Height);
 101
 102    /* The GL_ARB_viewport_array spec says:
 103     *
 104     *     "Viewport sets the parameters for all viewports to the same values
 105     *     and is equivalent (assuming no errors are generated) to:
 106     *
 107     *     for (uint i = 0; i < MAX_VIEWPORTS; i++)
 108     *         ViewportIndexedf(i, 1, (float)x, (float)y, (float)w, (float)h);"
 109     *
 110     * Set all of the viewports supported by the implementation, but only
 111     * signal the driver once at the end.
 112     */
 113    for (unsigned i = 0; i < ctx->Const.MaxViewports; i++)
 114       set_viewport_no_notify(ctx, i, input.X, input.Y, input.Width, input.Height);
 115
 116    if (ctx->Driver.Viewport)
 117       ctx->Driver.Viewport(ctx);
 118 }
 119
 120 /**
 121  * Set the viewport.
 122  * \sa Called via glViewport() or display list execution.
 123  *
 124  * Flushes the vertices and calls _mesa_set_viewport() with the given
 125  * parameters.
 126  */
 127 void GLAPIENTRY
 128 _mesa_Viewport_no_error(GLint x, GLint y, GLsizei width, GLsizei height)
 129 {
 130    GET_CURRENT_CONTEXT(ctx);
 131    viewport(ctx, x, y, width, height);
 132 }
 133
 134 void GLAPIENTRY
 135 _mesa_Viewport(GLint x, GLint y, GLsizei width, GLsizei height)
 136 {
 137    GET_CURRENT_CONTEXT(ctx);
 138
 139    if (MESA_VERBOSE & VERBOSE_API)
 140       _mesa_debug(ctx, "glViewport %d %d %d %d\n", x, y, width, height);
 141
 142    if (width < 0 || height < 0) {
 143       _mesa_error(ctx,  GL_INVALID_VALUE,
 144                    "glViewport(%d, %d, %d, %d)", x, y, width, height);
 145       return;
 146    }
 147
 148    viewport(ctx, x, y, width, height);
 149 }
 150
 151
 152 /**
 153  * Set new viewport parameters and update derived state.
 154  * Usually called from _mesa_Viewport().
 155  *
 156  * \param ctx GL context.
 157  * \param idx    Index of the viewport to be updated.
 158  * \param x, y coordinates of the lower left corner of the viewport rectangle.
 159  * \param width width of the viewport rectangle.
 160  * \param height height of the viewport rectangle.
 161  */
 162 void
 163 _mesa_set_viewport(struct gl_context *ctx, unsigned idx, GLfloat x, GLfloat y,
 164                     GLfloat width, GLfloat height)
 165 {
 166    clamp_viewport(ctx, &x, &y, &width, &height);
 167    set_viewport_no_notify(ctx, idx, x, y, width, height);
 168
 169    if (ctx->Driver.Viewport)
 170       ctx->Driver.Viewport(ctx);
 171 }
 172
 173 static void
 174 viewport_array(struct gl_context *ctx, GLuint first, GLsizei count,
 175                struct gl_viewport_inputs *inputs)
 176 {
 177    for (GLsizei i = 0; i < count; i++) {
 178       clamp_viewport(ctx, &inputs[i].X, &inputs[i].Y,
 179                      &inputs[i].Width, &inputs[i].Height);
 180
 181       set_viewport_no_notify(ctx, i + first, inputs[i].X, inputs[i].Y,
 182                              inputs[i].Width, inputs[i].Height);
 183    }
 184
 185    if (ctx->Driver.Viewport)
 186       ctx->Driver.Viewport(ctx);
 187 }
 188
 189 void GLAPIENTRY
 190 _mesa_ViewportArrayv_no_error(GLuint first, GLsizei count, const GLfloat *v)
 191 {
 192    GET_CURRENT_CONTEXT(ctx);
 193
 194    struct gl_viewport_inputs *p = (struct gl_viewport_inputs *)v;
 195    viewport_array(ctx, first, count, p);
 196 }
 197
 198 void GLAPIENTRY
 199 _mesa_ViewportArrayv(GLuint first, GLsizei count, const GLfloat *v)
 200 {
 201    int i;
 202    struct gl_viewport_inputs *p = (struct gl_viewport_inputs *)v;
 203    GET_CURRENT_CONTEXT(ctx);
 204
 205    if (MESA_VERBOSE & VERBOSE_API)
 206       _mesa_debug(ctx, "glViewportArrayv %d %d\n", first, count);
 207
 208    if ((first + count) > ctx->Const.MaxViewports) {
 209       _mesa_error(ctx, GL_INVALID_VALUE,
 210                   "glViewportArrayv: first (%d) + count (%d) > MaxViewports "
 211                   "(%d)",
 212                   first, count, ctx->Const.MaxViewports);
 213       return;
 214    }
 215
 216    /* Verify width & height */
 217    for (i = 0; i < count; i++) {
 218       if (p[i].Width < 0 || p[i].Height < 0) {
 219          _mesa_error(ctx, GL_INVALID_VALUE,
 220                      "glViewportArrayv: index (%d) width or height < 0 "
 221                      "(%f, %f)",
 222                      i + first, p[i].Width, p[i].Height);
 223          return;
 224       }
 225    }
 226
 227    viewport_array(ctx, first, count, p);
 228 }
 229
 230 static void
 231 viewport_indexed_err(struct gl_context *ctx, GLuint index, GLfloat x, GLfloat y,
 232                      GLfloat w, GLfloat h, const char *function)
 233 {
 234    if (MESA_VERBOSE & VERBOSE_API)
 235       _mesa_debug(ctx, "%s(%d, %f, %f, %f, %f)\n",
 236                   function, index, x, y, w, h);
 237
 238    if (index >= ctx->Const.MaxViewports) {
 239       _mesa_error(ctx, GL_INVALID_VALUE,
 240                   "%s: index (%d) >= MaxViewports (%d)",
 241                   function, index, ctx->Const.MaxViewports);
 242       return;
 243    }
 244
 245    /* Verify width & height */
 246    if (w < 0 || h < 0) {
 247       _mesa_error(ctx, GL_INVALID_VALUE,
 248                   "%s: index (%d) width or height < 0 (%f, %f)",
 249                   function, index, w, h);
 250       return;
 251    }
 252
 253    _mesa_set_viewport(ctx, index, x, y, w, h);
 254 }
 255
 256 void GLAPIENTRY
 257 _mesa_ViewportIndexedf_no_error(GLuint index, GLfloat x, GLfloat y,
 258                                 GLfloat w, GLfloat h)
 259 {
 260    GET_CURRENT_CONTEXT(ctx);
 261    _mesa_set_viewport(ctx, index, x, y, w, h);
 262 }
 263
 264 void GLAPIENTRY
 265 _mesa_ViewportIndexedf(GLuint index, GLfloat x, GLfloat y,
 266                        GLfloat w, GLfloat h)
 267 {
 268    GET_CURRENT_CONTEXT(ctx);
 269    viewport_indexed_err(ctx, index, x, y, w, h, "glViewportIndexedf");
 270 }
 271
 272 void GLAPIENTRY
 273 _mesa_ViewportIndexedfv_no_error(GLuint index, const GLfloat *v)
 274 {
 275    GET_CURRENT_CONTEXT(ctx);
 276    _mesa_set_viewport(ctx, index, v[0], v[1], v[2], v[3]);
 277 }
 278
 279 void GLAPIENTRY
 280 _mesa_ViewportIndexedfv(GLuint index, const GLfloat *v)
 281 {
 282    GET_CURRENT_CONTEXT(ctx);
 283    viewport_indexed_err(ctx, index, v[0], v[1], v[2], v[3],
 284                         "glViewportIndexedfv");
 285 }
 286
 287 static void
 288 set_depth_range_no_notify(struct gl_context *ctx, unsigned idx,
 289                           GLclampd nearval, GLclampd farval)
 290 {
 291    if (ctx->ViewportArray[idx].Near == nearval &&
 292        ctx->ViewportArray[idx].Far == farval)
 293       return;
 294
 295    /* The depth range is needed by program state constants. */
 296    FLUSH_VERTICES(ctx, _NEW_VIEWPORT);
 297    ctx->NewDriverState |= ctx->DriverFlags.NewViewport;
 298
 299    ctx->ViewportArray[idx].Near = CLAMP(nearval, 0.0, 1.0);
 300    ctx->ViewportArray[idx].Far = CLAMP(farval, 0.0, 1.0);
 301 }
 302
 303 void
 304 _mesa_set_depth_range(struct gl_context *ctx, unsigned idx,
 305                       GLclampd nearval, GLclampd farval)
 306 {
 307    set_depth_range_no_notify(ctx, idx, nearval, farval);
 308
 309    if (ctx->Driver.DepthRange)
 310       ctx->Driver.DepthRange(ctx);
 311 }
 312
 313 /**
 314  * Called by glDepthRange
 315  *
 316  * \param nearval  specifies the Z buffer value which should correspond to
 317  *                 the near clip plane
 318  * \param farval  specifies the Z buffer value which should correspond to
 319  *                the far clip plane
 320  */
 321 void GLAPIENTRY
 322 _mesa_DepthRange(GLclampd nearval, GLclampd farval)
 323 {
 324    unsigned i;
 325    GET_CURRENT_CONTEXT(ctx);
 326
 327    if (MESA_VERBOSE&VERBOSE_API)
 328       _mesa_debug(ctx, "glDepthRange %f %f\n", nearval, farval);
 329
 330    /* The GL_ARB_viewport_array spec says:
 331     *
 332     *     "DepthRange sets the depth range for all viewports to the same
 333     *     values and is equivalent (assuming no errors are generated) to:
 334     *
 335     *     for (uint i = 0; i < MAX_VIEWPORTS; i++)
 336     *         DepthRangeIndexed(i, n, f);"
 337     *
 338     * Set the depth range for all of the viewports supported by the
 339     * implementation, but only signal the driver once at the end.
 340     */
 341    for (i = 0; i < ctx->Const.MaxViewports; i++)
 342       set_depth_range_no_notify(ctx, i, nearval, farval);
 343
 344    if (ctx->Driver.DepthRange) {
 345       ctx->Driver.DepthRange(ctx);
 346    }
 347 }
 348
 349 void GLAPIENTRY
 350 _mesa_DepthRangef(GLclampf nearval, GLclampf farval)
 351 {
 352    _mesa_DepthRange(nearval, farval);
 353 }
 354
 355 /**
 356  * Update a range DepthRange values
 357  *
 358  * \param first   starting array index
 359  * \param count   count of DepthRange items to update
 360  * \param v       pointer to memory containing
 361  *                GLclampd near and far clip-plane values
 362  */
 363 static ALWAYS_INLINE void
 364 depth_range_arrayv(struct gl_context *ctx, GLuint first, GLsizei count,
 365                    const struct gl_depthrange_inputs *const inputs)
 366 {
 367    for (GLsizei i = 0; i < count; i++)
 368       set_depth_range_no_notify(ctx, i + first, inputs[i].Near, inputs[i].Far);
 369
 370    if (ctx->Driver.DepthRange)
 371       ctx->Driver.DepthRange(ctx);
 372 }
 373
 374 void GLAPIENTRY
 375 _mesa_DepthRangeArrayv_no_error(GLuint first, GLsizei count, const GLclampd *v)
 376 {
 377    GET_CURRENT_CONTEXT(ctx);
 378
 379    const struct gl_depthrange_inputs *const p =
 380       (struct gl_depthrange_inputs *)v;
 381    depth_range_arrayv(ctx, first, count, p);
 382 }
 383
 384 void GLAPIENTRY
 385 _mesa_DepthRangeArrayv(GLuint first, GLsizei count, const GLclampd *v)
 386 {
 387    const struct gl_depthrange_inputs *const p =
 388       (struct gl_depthrange_inputs *) v;
 389    GET_CURRENT_CONTEXT(ctx);
 390
 391    if (MESA_VERBOSE & VERBOSE_API)
 392       _mesa_debug(ctx, "glDepthRangeArrayv %d %d\n", first, count);
 393
 394    if ((first + count) > ctx->Const.MaxViewports) {
 395       _mesa_error(ctx, GL_INVALID_VALUE,
 396                   "glDepthRangev: first (%d) + count (%d) >= MaxViewports (%d)",
 397                   first, count, ctx->Const.MaxViewports);
 398       return;
 399    }
 400
 401    depth_range_arrayv(ctx, first, count, p);
 402 }
 403
 404 void GLAPIENTRY
 405 _mesa_DepthRangeArrayfvOES(GLuint first, GLsizei count, const GLfloat *v)
 406 {
 407    int i;
 408    GET_CURRENT_CONTEXT(ctx);
 409
 410    if (MESA_VERBOSE & VERBOSE_API)
 411       _mesa_debug(ctx, "glDepthRangeArrayfv %d %d\n", first, count);
 412
 413    if ((first + count) > ctx->Const.MaxViewports) {
 414       _mesa_error(ctx, GL_INVALID_VALUE,
 415                   "glDepthRangeArrayfv: first (%d) + count (%d) >= MaxViewports (%d)",
 416                   first, count, ctx->Const.MaxViewports);
 417       return;
 418    }
 419
 420    for (i = 0; i < count; i++)
 421       set_depth_range_no_notify(ctx, i + first, v[i * 2], v[i * 2 + 1]);
 422
 423    if (ctx->Driver.DepthRange)
 424       ctx->Driver.DepthRange(ctx);
 425 }
 426
 427 /**
 428  * Update a single DepthRange
 429  *
 430  * \param index    array index to update
 431  * \param nearval  specifies the Z buffer value which should correspond to
 432  *                 the near clip plane
 433  * \param farval   specifies the Z buffer value which should correspond to
 434  *                 the far clip plane
 435  */
 436 void GLAPIENTRY
 437 _mesa_DepthRangeIndexed_no_error(GLuint index, GLclampd nearval,
 438                                  GLclampd farval)
 439 {
 440    GET_CURRENT_CONTEXT(ctx);
 441    _mesa_set_depth_range(ctx, index, nearval, farval);
 442 }
 443
 444
 445 void GLAPIENTRY
 446 _mesa_DepthRangeIndexed(GLuint index, GLclampd nearval, GLclampd farval)
 447 {
 448    GET_CURRENT_CONTEXT(ctx);
 449
 450    if (MESA_VERBOSE & VERBOSE_API)
 451       _mesa_debug(ctx, "glDepthRangeIndexed(%d, %f, %f)\n",
 452                   index, nearval, farval);
 453
 454    if (index >= ctx->Const.MaxViewports) {
 455       _mesa_error(ctx, GL_INVALID_VALUE,
 456                   "glDepthRangeIndexed: index (%d) >= MaxViewports (%d)",
 457                   index, ctx->Const.MaxViewports);
 458       return;
 459    }
 460
 461    _mesa_set_depth_range(ctx, index, nearval, farval);
 462 }
 463
 464 void GLAPIENTRY
 465 _mesa_DepthRangeIndexedfOES(GLuint index, GLfloat nearval, GLfloat farval)
 466 {
 467    _mesa_DepthRangeIndexed(index, nearval, farval);
 468 }
 469
 470 /**
 471  * Initialize the context viewport attribute group.
 472  * \param ctx  the GL context.
 473  */
 474 void _mesa_init_viewport(struct gl_context *ctx)
 475 {
 476    unsigned i;
 477
 478    ctx->Transform.ClipOrigin = GL_LOWER_LEFT;
 479    ctx->Transform.ClipDepthMode = GL_NEGATIVE_ONE_TO_ONE;
 480
 481    /* Note: ctx->Const.MaxViewports may not have been set by the driver yet,
 482     * so just initialize all of them.
 483     */
 484    for (i = 0; i < MAX_VIEWPORTS; i++) {
 485       /* Viewport group */
 486       ctx->ViewportArray[i].X = 0;
 487       ctx->ViewportArray[i].Y = 0;
 488       ctx->ViewportArray[i].Width = 0;
 489       ctx->ViewportArray[i].Height = 0;
 490       ctx->ViewportArray[i].Near = 0.0;
 491       ctx->ViewportArray[i].Far = 1.0;
 492    }
 493 }
 494
 495
 496 static ALWAYS_INLINE void
 497 clip_control(struct gl_context *ctx, GLenum origin, GLenum depth, bool no_error)
 498 {
 499    if (ctx->Transform.ClipOrigin == origin &&
 500        ctx->Transform.ClipDepthMode == depth)
 501       return;
 502
 503    if (!no_error &&
 504        origin != GL_LOWER_LEFT && origin != GL_UPPER_LEFT) {
 505       _mesa_error(ctx, GL_INVALID_ENUM, "glClipControl");
 506       return;
 507    }
 508
 509    if (!no_error &&
 510        depth != GL_NEGATIVE_ONE_TO_ONE && depth != GL_ZERO_TO_ONE) {
 511       _mesa_error(ctx, GL_INVALID_ENUM, "glClipControl");
 512       return;
 513    }
 514
 515    /* Affects transform state and the viewport transform */
 516    FLUSH_VERTICES(ctx, ctx->DriverFlags.NewClipControl ? 0 :
 517                   _NEW_TRANSFORM | _NEW_VIEWPORT);
 518    ctx->NewDriverState |= ctx->DriverFlags.NewClipControl;
 519
 520    if (ctx->Transform.ClipOrigin != origin) {
 521       ctx->Transform.ClipOrigin = origin;
 522
 523       /* Affects the winding order of the front face. */
 524       if (ctx->DriverFlags.NewPolygonState)
 525          ctx->NewDriverState |= ctx->DriverFlags.NewPolygonState;
 526       else
 527          ctx->NewState |= _NEW_POLYGON;
 528
 529       if (ctx->Driver.FrontFace)
 530          ctx->Driver.FrontFace(ctx, ctx->Polygon.FrontFace);
 531    }
 532
 533    if (ctx->Transform.ClipDepthMode != depth) {
 534       ctx->Transform.ClipDepthMode = depth;
 535
 536       if (ctx->Driver.DepthRange)
 537          ctx->Driver.DepthRange(ctx);
 538    }
 539 }
 540
 541
 542 void GLAPIENTRY
 543 _mesa_ClipControl_no_error(GLenum origin, GLenum depth)
 544 {
 545    GET_CURRENT_CONTEXT(ctx);
 546    clip_control(ctx, origin, depth, true);
 547 }
 548
 549
 550 void GLAPIENTRY
 551 _mesa_ClipControl(GLenum origin, GLenum depth)
 552 {
 553    GET_CURRENT_CONTEXT(ctx);
 554
 555    if (MESA_VERBOSE & VERBOSE_API)
 556       _mesa_debug(ctx, "glClipControl(%s, %s)\n",
 557                   _mesa_enum_to_string(origin),
 558                   _mesa_enum_to_string(depth));
 559
 560    ASSERT_OUTSIDE_BEGIN_END(ctx);
 561
 562    if (!ctx->Extensions.ARB_clip_control) {
 563       _mesa_error(ctx, GL_INVALID_OPERATION, "glClipControl");
 564       return;
 565    }
 566
 567    clip_control(ctx, origin, depth, false);
 568 }
 569
 570 /**
 571  * Computes the scaling and the translation part of the
 572  * viewport transform matrix of the \param i-th viewport
 573  * and writes that into \param scale and \param translate.
 574  */
 575 void
 576 _mesa_get_viewport_xform(struct gl_context *ctx, unsigned i,
 577                          float scale[3], float translate[3])
 578 {
 579    float x = ctx->ViewportArray[i].X;
 580    float y = ctx->ViewportArray[i].Y;
 581    float half_width = 0.5f * ctx->ViewportArray[i].Width;
 582    float half_height = 0.5f * ctx->ViewportArray[i].Height;
 583    double n = ctx->ViewportArray[i].Near;
 584    double f = ctx->ViewportArray[i].Far;
 585
 586    scale[0] = half_width;
 587    translate[0] = half_width + x;
 588    if (ctx->Transform.ClipOrigin == GL_UPPER_LEFT) {
 589       scale[1] = -half_height;
 590    } else {
 591       scale[1] = half_height;
 592    }
 593    translate[1] = half_height + y;
 594
 595    if (ctx->Transform.ClipDepthMode == GL_NEGATIVE_ONE_TO_ONE) {
 596       scale[2] = 0.5 * (f - n);
 597       translate[2] = 0.5 * (n + f);
 598    } else {
 599       scale[2] = f - n;
 600       translate[2] = n;
 601    }
 602 }