Merge pull request #3889 from akohlmey/image-anti-alias

Implement anti-aliasing for dump image (and dump movie)

doc/src/dump_image.rst

@@ -24,7 +24,7 @@ Syntax
 * color = atom attribute that determines color of each atom
 * diameter = atom attribute that determines size of each atom
 * zero or more keyword/value pairs may be appended
-* keyword = *atom* or *adiam* or *bond* or *grid* or *line* or *tri* or *body* or *fix* or *size* or *view* or *center* or *up* or *zoom* or *box* or *axes* or *subbox* or *shiny* or *ssao*
+* keyword = *atom* or *adiam* or *bond* or *grid* or *line* or *tri* or *body* or *fix* or *size* or *view* or *center* or *up* or *zoom* or *box* or *axes* or *subbox* or *shiny* or *fsaa* or *ssao*
 
   .. parsed-literal::
 
@@ -85,6 +85,8 @@ Syntax
          diam = diameter of subdomain lines as fraction of shortest box length
        *shiny* value = sfactor = shinyness of spheres and cylinders
          sfactor = shinyness of spheres and cylinders from 0.0 to 1.0
+       *fsaa* arg = yes/no
+         yes/no = do or do not apply anti-aliasing
        *ssao* value = shading seed dfactor = SSAO depth shading
          shading = *yes* or *no* = turn depth shading on/off
          seed = random # seed (positive integer)
@@ -227,7 +229,7 @@ details have to be looked up in the `FFmpeg documentation
 described below.
 
 To write out JPEG and PNG format files, you must build LAMMPS with
-support for the corresponding JPEG or PNG library. To convert images
+support for the corresponding JPEG or PNG library.  To convert images
 into movies, LAMMPS has to be compiled with the -DLAMMPS_FFMPEG
 flag. See the :doc:`Build settings <Build_settings>` page for
 details.
@@ -597,13 +599,47 @@ image will appear.  The *sfactor* value must be a value 0.0 <=
 *sfactor* <= 1.0, where *sfactor* = 1 is a highly reflective surface
 and *sfactor* = 0 is a rough non-shiny surface.
 
-The *ssao* keyword turns on/off a screen space ambient occlusion
-(SSAO) model for depth shading.  If *yes* is set, then atoms further
-away from the viewer are darkened via a randomized process, which is
-perceived as depth.  The calculation of this effect can increase the
-cost of computing the image by roughly 2x.  The strength of the effect
-can be scaled by the *dfactor* parameter.  If *no* is set, no depth
-shading is performed.
+.. versionadded:: TBD
+
+The *fsaa* keyword can be used with the dump image command to improve
+the image quality by enabling full scene anti-aliasing.  Internally the
+image is rendered at twice the width and height and then scaled down by
+computing the average of each 2x2 block of pixels to produce a single
+pixel in the final image at the original size. This produces images with
+smoother, less ragged edges.  The application of this algorithm can
+increase the cost of computing the image by about 3x or more.
+
+The *ssao* keyword turns on/off a screen space ambient occlusion (SSAO)
+model for depth shading.  If *yes* is set, then atoms further away from
+the viewer are darkened via a randomized process, which is perceived as
+depth.  The strength of the effect can be scaled by the *dfactor*
+parameter.  If *no* is set, no depth shading is performed.  The
+calculation of this effect can increase the cost of computing the image
+substantially by 5x or more, especially with larger images.  When used
+in combination with the *fsaa* keyword the computational cost of depth
+shading is particularly large.
+
+----------
+
+Image Quality Settings
+""""""""""""""""""""""
+
+The two keywords *fsaa* and *ssao* can be used to improve the image
+quality at the expense of additional computational cost to render the
+images. The images below show from left to right the same render with
+default settings, with *fsaa* added, with *ssao* added, and with both
+keywords added.
+
+.. |imagequality1| image:: JPG/image.default.png
+   :width: 24%
+.. |imagequality2| image:: JPG/image.fsaa.png
+   :width: 24%
+.. |imagequality3| image:: JPG/image.ssao.png
+   :width: 24%
+.. |imagequality4| image:: JPG/image.both.png
+   :width: 24%
+
+|imagequality1|  |imagequality2|  |imagequality3|  |imagequality4|
 
 ----------
 
@@ -1051,6 +1087,7 @@ The defaults for the dump_modify keywords specific to dump image and dump movie
 * boxcolor = yellow
 * color = 140 color names are pre-defined as listed below
 * framerate = 24
+* fsaa = no
 * gmap = min max cf 0.0 2 min blue max red
 
 ----------

doc/utils/sphinx-config/false_positives.txt

@@ -1195,6 +1195,7 @@ Freitas
 Frenkel
 Friedrichs
 fs
+fsaa
 fsh
 fstyle
 fsw

src/dump_image.cpp

@@ -248,10 +248,14 @@ DumpImage::DumpImage(LAMMPS *lmp, int narg, char **arg) :
       if (iarg+3 > narg) error->all(FLERR,"Illegal dump image command");
       int width = utils::inumeric(FLERR,arg[iarg+1],false,lmp);
       int height = utils::inumeric(FLERR,arg[iarg+2],false,lmp);
-      if (width <= 0 || height <= 0)
-        error->all(FLERR,"Illegal dump image command");
-      image->width = width;
-      image->height = height;
+      if (width <= 0 || height <= 0) error->all(FLERR,"Illegal dump image command");
+      if (image->fsaa) {
+        image->width = width*2;
+        image->height = height*2;
+      } else {
+        image->width = width;
+        image->height = height;
+      }
       iarg += 3;
 
     } else if (strcmp(arg[iarg],"view") == 0) {
@@ -345,6 +349,23 @@ DumpImage::DumpImage(LAMMPS *lmp, int narg, char **arg) :
       image->shiny = shiny;
       iarg += 2;
 
+    } else if (strcmp(arg[iarg],"fsaa") == 0) {
+      if (iarg+2 > narg) error->all(FLERR,"Illegal dump_modify command");
+      int aa = utils::logical(FLERR, arg[iarg+1], false, lmp);
+      if (aa) {
+        if (!image->fsaa) {
+          image->width = image->width*2;
+          image->height = image->height*2;
+        }
+      } else {
+        if (image->fsaa) {
+          image->width = image->width/2;
+          image->height = image->height/2;
+        }
+      }
+      image->fsaa = aa;
+      iarg += 2;
+
     } else if (strcmp(arg[iarg],"ssao") == 0) {
       if (iarg+4 > narg) error->all(FLERR,"Illegal dump image command");
       image->ssao = utils::logical(FLERR,arg[iarg+1],false,lmp);

src/image.cpp

@@ -55,7 +55,9 @@ enum{NO,YES};
 
 /* ---------------------------------------------------------------------- */
 
-Image::Image(LAMMPS *lmp, int nmap_caller) : Pointers(lmp)
+Image::Image(LAMMPS *lmp, int nmap_caller) :
+    Pointers(lmp), depthBuffer(nullptr), surfaceBuffer(nullptr), depthcopy(nullptr),
+    surfacecopy(nullptr), imageBuffer(nullptr), rgbcopy(nullptr), writeBuffer(nullptr)
 {
   MPI_Comm_rank(world,&me);
   MPI_Comm_size(world,&nprocs);
@@ -69,6 +71,7 @@ Image::Image(LAMMPS *lmp, int nmap_caller) : Pointers(lmp)
   persp = 0.0;
   shiny = 1.0;
   ssao = NO;
+  fsaa = NO;
 
   up[0] = 0.0;
   up[1] = 0.0;
@@ -154,6 +157,13 @@ Image::~Image()
 
 void Image::buffers()
 {
+  memory->destroy(depthBuffer);
+  memory->destroy(surfaceBuffer);
+  memory->destroy(imageBuffer);
+  memory->destroy(depthcopy);
+  memory->destroy(surfacecopy);
+  memory->destroy(rgbcopy);
+
   npixels = width * height;
   memory->create(depthBuffer,npixels,"image:depthBuffer");
   memory->create(surfaceBuffer,2*npixels,"image:surfaceBuffer");
@@ -380,6 +390,26 @@ void Image::merge()
   } else {
     writeBuffer = imageBuffer;
   }
+
+  // scale down image for antialiasing. can be done in place with simple averaging
+  if (fsaa) {
+    for (int h=0; h < height; h += 2) {
+      for (int w=0; w < width; w +=2) {
+        int idx1 = 3*height*h + 3*w;
+        int idx2 = 3*height*h + 3*(w+1);
+        int idx3 = 3*height*(h+1) + 3*w;
+        int idx4 = 3*height*(h+1) + 3*(w+1);
+
+        int out = 3*(height/2)*(h/2) + 3*(w/2);
+        for (int i=0; i < 3; ++i) {
+          writeBuffer[out+i] = (unsigned char) (0.25*((int)writeBuffer[idx1+i]
+                                                      +(int)writeBuffer[idx2+i]
+                                                      +(int)writeBuffer[idx3+i]
+                                                      +(int)writeBuffer[idx4+i]));
+        }
+      }
+    }
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -1037,6 +1067,7 @@ void Image::compute_SSAO()
 void Image::write_JPG(FILE *fp)
 {
 #ifdef LAMMPS_JPEG
+  int aafactor = fsaa ? 2 : 1;
   struct jpeg_compress_struct cinfo;
   struct jpeg_error_mgr jerr;
   JSAMPROW row_pointer;
@@ -1044,8 +1075,8 @@ void Image::write_JPG(FILE *fp)
   cinfo.err = jpeg_std_error(&jerr);
   jpeg_create_compress(&cinfo);
   jpeg_stdio_dest(&cinfo,fp);
-  cinfo.image_width = width;
-  cinfo.image_height = height;
+  cinfo.image_width = width/aafactor;
+  cinfo.image_height = height/aafactor;
   cinfo.input_components = 3;
   cinfo.in_color_space = JCS_RGB;
 
@@ -1055,7 +1086,7 @@ void Image::write_JPG(FILE *fp)
 
   while (cinfo.next_scanline < cinfo.image_height) {
     row_pointer = (JSAMPROW)
-      &writeBuffer[(cinfo.image_height - 1 - cinfo.next_scanline) * 3 * width];
+      &writeBuffer[(cinfo.image_height - 1 - cinfo.next_scanline) * 3 * (width/aafactor)];
     jpeg_write_scanlines(&cinfo,&row_pointer,1);
   }
 
@@ -1071,6 +1102,7 @@ void Image::write_JPG(FILE *fp)
 void Image::write_PNG(FILE *fp)
 {
 #ifdef LAMMPS_PNG
+  int aafactor = fsaa ? 2 : 1;
   png_structp png_ptr;
   png_infop info_ptr;
 
@@ -1090,8 +1122,8 @@ void Image::write_PNG(FILE *fp)
   }
 
   png_init_io(png_ptr, fp);
-  png_set_compression_level(png_ptr,Z_BEST_COMPRESSION);
-  png_set_IHDR(png_ptr,info_ptr,width,height,8,PNG_COLOR_TYPE_RGB,
+  png_set_compression_level(png_ptr,Z_BEST_SPEED);
+  png_set_IHDR(png_ptr,info_ptr,width/aafactor,height/aafactor,8,PNG_COLOR_TYPE_RGB,
     PNG_INTERLACE_NONE,PNG_COMPRESSION_TYPE_DEFAULT,PNG_FILTER_TYPE_DEFAULT);
 
   png_text text_ptr[2];
@@ -1111,9 +1143,9 @@ void Image::write_PNG(FILE *fp)
   png_set_text(png_ptr,info_ptr,text_ptr,1);
   png_write_info(png_ptr,info_ptr);
 
-  auto row_pointers = new png_bytep[height];
-  for (int i=0; i < height; ++i)
-    row_pointers[i] = (png_bytep) &writeBuffer[(height-i-1)*3*width];
+  auto row_pointers = new png_bytep[height/aafactor];
+  for (int i=0; i < height/aafactor; ++i)
+    row_pointers[i] = (png_bytep) &writeBuffer[((height/aafactor)-i-1)*3*(width/aafactor)];
 
   png_write_image(png_ptr, row_pointers);
   png_write_end(png_ptr, info_ptr);
@@ -1129,11 +1161,12 @@ void Image::write_PNG(FILE *fp)
 
 void Image::write_PPM(FILE *fp)
 {
-  fprintf(fp,"P6\n%d %d\n255\n",width,height);
+  int aafactor = fsaa ? 2 : 1;
+  fprintf(fp,"P6\n%d %d\n255\n",width/aafactor,height/aafactor);
 
   int y;
-  for (y = height-1; y >= 0; y--)
-    fwrite(&writeBuffer[y*width*3],3,width,fp);
+  for (y = (height/aafactor)-1; y >= 0; y--)
+    fwrite(&writeBuffer[y*(width/aafactor)*3],3,width/aafactor,fp);
 }
 
 /* ----------------------------------------------------------------------

src/image.h

@@ -28,13 +28,14 @@ class Image : protected Pointers {
   double zoom;                // zoom factor
   double persp;               // perspective factor
   double shiny;               // shininess of objects
+  int fsaa;                   // antialiasing on or off
   int ssao;                   // SSAO on or off
   int seed;                   // RN seed for SSAO
   double ssaoint;             // strength of shading from 0 to 1
   double *boxcolor;           // color to draw box outline with
   int background[3];          // RGB values of background
 
-  double ambientColor[3];     // light color settings (adjustable by caller)
+  double ambientColor[3];    // light color settings (adjustable by caller)
   double keyLightColor[3];
   double fillLightColor[3];
   double backLightColor[3];